生物组织脱水过程的太赫兹时域光谱

利用透射式太赫兹时域光谱(THz-TDS)技术对猪脂肪、肌肉和皮肤三种新鲜组织的持续脱水过程进行在线连续扫描,观察太赫兹波时域谱在组织脱水过程的变化,并分析比较三种组织脱水前后的太赫兹波吸收系数及折射率的改变及差异.结果表明,太赫兹波对新鲜组织含水量的改变十分敏感,新鲜组织的含水量是影响太赫兹波吸收系数的主要因素.同时,不同组织对太赫兹的吸收有明显差异,表明太赫兹光谱技术可以鉴别不同的组织类型.本研究为太赫兹技术在生物医学领域的进一步研究和应用提供了帮助.     

用于太赫兹光谱测量的土壤样品压片制备方法研究

太赫兹技术是信息科学领域迅速发展起来的新兴科技,太赫兹波与物质之间的相互作用机理有待深入挖掘。在太赫兹光谱测量前需对样品进行预处理,为利用太赫兹技术进行土壤样品的理化参数研究,开展了用于太赫兹时域光谱测量的土壤样品压片法制备研究,分析了压片制备过程中存在的问题,优化了制备工艺,并以样品质量(130 mg、180 mg、220 mg、280 mg、330 mg、400 mg)和外界压力(0.5~5 t每隔0.5 t一个压力,1 t=1000 kg)为变量进行了适合于太赫兹光谱测量的土壤样品压片制备参数选择的实验探索,确立了以220 mg/片,2.5 t压力为土壤样品压片的最佳制备参数。该研究为土壤样品理化参数采用压片法进行后续太赫兹测试实验提供了有效的原始数据,为其他固体样本制备和太赫兹光谱数据测量提供了科学的方法参考。     

基于太赫兹辐射的甘草主成分光谱分析

采用透射式太赫兹时域光谱系统测试了甘草主成分甘草酸、甘草次酸以及甘草苷的太赫兹光谱,发现甘草酸、甘草次酸以及甘草苷在0.3～1.72 THz频段内具有明显的吸收特征,此频段内它们的太赫兹吸收峰峰位接近、吸收谱谱线相似.利用量子化学方法模拟甘草酸的太赫兹吸收谱,并与实验谱进行对比指认完成对3种单质的定性分析工作.本文分别...     

太赫兹场作用下半导体超晶格的动力学过程及光吸收谱研究

基于激子基，采用密度矩阵理论研究了太赫兹场作用下半导体超晶格的子带间动力学过程及光吸收谱。在太赫兹场的驱动下，激子作布洛赫振荡。子带间极化的缓慢变化依赖于太赫兹频率，随着太赫兹频率的增加，子带间极化向下振荡，极化强度降低。以 和 两种超晶格为例进行研究，它们的光吸收谱出现了卫星峰结构，这是由于太赫兹场与万尼尔斯塔克阶梯激子作用的非线性效应产生的。但是就 与 超晶格相比而言，我们研究发现，n<0的激子态与n=0的激子态耦合作用较强使得光吸收谱吻合性较好，n＝0时的激子态吸收光谱出现红移，n>0的激子态光吸收谱中出现的边带效应不是很明显。     

钝感RDX及HMX炸药的太赫兹光谱分析

采用太赫兹时域光谱技术（Terahertz time-domain spectroscopy,THz-TDS）对钝感RDX（黑索金）和HMX（奥克托金）炸药在0～2.5THz频段的太赫兹吸收光谱进行了探测.得到了待测样品的太赫兹吸收光谱,确定了其特征吸收峰的位置并与其他研究机构所测吸收谱进行了对比分析.实验结果表明：利用THz-TDS技术可以对炸药进行检测和识别,同时可以对样品组成的细微变化进行分析和鉴别.为利用THz-TDS技术研究其他爆炸性物质,建立爆炸物的指纹谱库提供了科学依据.     

THz Spectroscopic Identification of Red Mineral Pigments in Ancient Chinese Artworks

Nondestructive analysis of historical objects is of significance for cultural heritage conservation. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to distinguish seven red mineral pigments used in ancient Chinese artworks. Two absorption features of natural minerals HgS and four highly resolved spectral features of mineral pigment Pb₃O₄ were observed and identified as their fingerprints in the range 0.2 to 3.0 THz, based on which the spatial distribution of individual chemical substances including cinnabar, vermilion, and red lead were clearly revealed at various frequencies using terahertz spectroscopy imaging. Moreover, a noncontact evaluation of thickness changing and dehydration of a wet painting was monitored by inferring time delay as well as signal amplitude of THz pulses transmitted through the painting. In order to demonstrate the feasibility of THz-TDS and THz imaging for authentic artworks detection, a complete set of THz analysis of two nineteenth century wall paintings discovered in the Fuchen Temple of the Forbidden City, Beijing, was performed and the results indicate that THz measurement techniques provide a noninvasive and nondestructive solution for the care, preservation, and restoration of cultural relics.     

太赫兹技术的液体中同型半胱氨酸的定量识别研究

同型半胱氨酸是一种含硫氨基酸,为蛋氨酸和半胱氨酸代谢过程中产生的重要中间产物,它在人体血液或尿液中浓度含量过高时会大幅增加心血管疾病、老年痴呆、骨折等疾病的发病风险。基于太赫兹时域光谱系统,针对液体状态下同型半胱氨酸的检测提出了浓缩富集再烘干的处理方法,有效测量了不同浓度下同型半胱氨酸的太赫兹吸收光谱。经过与拉曼光谱方法的结果比对,证明太赫兹检测的精度比拉曼光谱检测的精度提升了3倍。该结果对临床医学中同型半胱氨酸相关疾病的准确、快速诊断具有重要意义。     

太赫兹应用分析和展望

以6G需求为抓手引入了太赫兹技术,介绍了太赫兹的研究背景和国内外研究现状。之后结合太赫兹的频谱范围,对太赫兹频段和毫米波以及红外光进行了详细对比分析,发现了太赫兹特有的一些频谱特性,包括宽带性、低能性、电磁特性和特征谱等,并进一步挖掘基于这些频谱特性的应用,研究表明,太赫兹未来可应用于军事、医疗、检测和通信等诸多领域,对于仍存在的挑战和瓶颈,中国联通将联合产业界一同推动解决,最大化发挥太赫兹应用潜力。     

光敏自组装单层膜用于液晶光控取向的研究

用丁二酸酐和7-羟基香豆素合成了含有脂肪族羧酸基团的光敏化合物，利用脱水反应使它在玻璃(或石英)基板表面形成自组装单层膜。用偏振紫外光照射光敏性自组装膜，与光矢量方向匹配的香豆素基团发生[2 2]周环反应，反应产物沿辐照光的偏振方向分布，形成表面张力各向异性的薄膜。用它作为向列相液晶取向膜制成平行液晶器件，在偏光显微镜下观察，发现取得了均一、稳定的取向效果。并且该取向膜有良好的热稳定性。     

Spectrum Determination of Terahertz Sources Using Fabry-Perot Interferometer and Bolometer Detector

We describe a method to determine the radiation spectrum of terahertz sources using a transmitted Fabry-Perot interferometer and a bolometer detector. Our novel Fabry-Perot spectrometer can measure the spectrum of an unknown broadband sub-terahertz and terahertz source. The spectrometer does not need to be pre-tuned. We develop a new algorithm to support the measurements using this spectrometer. Our technique allows us to measure the spectrum over more than an octave, and our numerical algorithm is very stable and robust, providing for an accurate spectrum determination. Two Gunn oscillation sources with the main frequencies at 200 GHz and 600 GHz are used to test the proposed method. The spectrum extracted from the measured data shows that this method is accurate and reliable.     

无线通信应用太赫兹技术研究进展

在过去的几年里,由于不同频段电磁频谱的传播特性差异、对带宽需求以及技术利用能力提升,无线通信应用的电磁频谱不断提高。在通信领域,为满足无线数据传输需求的爆炸性增长,特别是5G通信的发展,毫米波中低频段应用已经成功实现工程化并开始商业化。而对于以光波为载体的更高频率电磁波的光通信,也已经发展了几十年。在常规无线电波(毫米波)与常规光学(远红外)之间,存在着一段长期未能有效利用的空闲频谱资源,目前被统称为太赫兹频段(0.1~10 THz)。太赫兹频段在高速无线通信领域具备明显优势,成为有潜力的6G通信核心技术。可以预见,对这项技术的使用将助力6G通信实现网络全覆盖、高度智能化及网络安全性全面提升的愿景。文章主要关注通信领域,重点介绍了太赫兹频段的特点、构建太赫兹系统功能的器件类型与工艺集成实现技术。最后,预测了太赫兹通信技术的一些应用场景,进而显示出该技术对通信领域和人们日常生活的促进作用。     

硫酸镁水合物的太赫兹表征

太赫兹时域光谱技术作为一种新型光谱检测手段,可用于包括水合物在内的多种物质的表征。金属硫酸盐具有多种不同的水合物,在太赫兹波段表现出不同的吸收特性,利用太赫兹光谱技术可以对过渡金属硫酸盐的不同水合物进行有效表征。本文利用太赫兹时域光谱系统对硫酸镁及其水合物进行表征。通过对七水硫酸镁进行恒温干燥,得到不同的硫酸镁热解产物并对其太赫兹吸收光谱进行研究。实验结果表明不同水合物表现出差异明显的太赫兹吸收特性。这为硫酸镁水合物的多种应用提供了重要参考,也为过渡金属硫酸盐及其水合物的检测提供了简单、快捷、有效的表征手段。     

太赫兹感知通信一体化波形设计与信号处理

太赫兹波段感知通信一体化技术能够在提高数据传输速率和感知分辨率的同时,有效降低硬件资源和频谱资源的消耗。首先,简要介绍了感知通信一体化及太赫兹通信、感知的现状。然后,分别从感知和通信的角度讨论了一体化波形设计及优化策略,同时分析了两类信号接收机的信号处理算法,并实验展示了一种97GHz基于OFDM信号的一体化系统,对系统的距离、速度和通信等性能进行了测试。最后,总结和展望了太赫兹感知通信一体化的技术难题和未来研究方向。     

ZnTe晶体对太赫兹波的电光响应及极化匹配

给出了ZnTe电光晶体折射率和吸收系数随太赫兹波频率而变化的计算曲线,比较了太赫兹波在ZnTe中传播时的相速度和群速度。通过与太赫兹频率和晶体厚度相关的电光效率响应函数,理论计算了ZnTe电光晶体对太赫兹脉冲的探测电光响应,得到了晶体厚度与探测到的太赫兹频谱宽度的定性关系,从计算结果中找到了ZnTe电光晶体在5.3 THz和6.2 THz等多个频点的探测盲点,这些探测盲点来自于ZnTe电光晶体与相应频点太赫兹波的栅格共振吸收。结合自制的大口径太赫兹光导天线和1 kHz脉冲重复频率的太赫兹时域光谱实验系统,通过差分探测技术,从实验上得到了太赫兹波极化方向与〈110〉型ZnTe晶体晶轴方向的六个最佳匹配角度,给出了太赫兹电场最大值随晶轴与太赫兹波极化方向之间夹角变化的曲线及经验公式,这将有利于在实践中对该现象的深入理解和对探测灵敏度的有效提高。     

太赫兹波的几个基本问题

介绍了用于加工太赫兹波元件的微机械加工技术(铣削、放电加工、电铸、湿法腐蚀Si、干法腐蚀Si、厚光刻胶:SU-8和LIGA)及其最新结果。重点描述了应用于太赫兹波的器件和集成电路,如将可用于太赫兹波的各种新颖二极管、半导体纳米器件、新的高电子迁移率晶体管、毫米波集成电路、量子器件、红外器件、量子级联激光器(单极级间跃迁激光器)。基于带间跃迁量子机理的半导体器件(譬如量子级联激光器)的频率极限高于与半导体能带隙相关器件的频率,其大多数体半导体的频率可以达到10THz以上。但是,基于经典的电子扩散传输机理的二极管、三极管的高频极限则受限于渡越时间和寄生参数RC时间常数。     

Microribbon‐Like Elastomers for Fabricating Macroporous and Highly Flexible Scaffolds that Support Cell Proliferation in 3D

Hydrogel‐based scaffolds are widely used for culturing cells in three dimensions due to their tissue‐like water content and tunable biochemical and physical properties. Most conventional hydrogels lack the macroporosity desirable for efficient cell proliferation and migration and have limited flexibility when subject to mechanical load. Here microribbon‐like elastomers that, when photocrosslinked, can form macroporous and highly flexible scaffolds that support cell proliferation in 3D are developed. These microribbons are produced by wet‐spinning gelatin solution into microfibers, followed by drying in acetone, which causes asymmetrical collapse of microfibers to form microribbon‐like structures. Gelatin microribbons are then modified using methacrylate anhydride to allow further photocrosslinking into 3D scaffolds. The macroporosity and mechanical properties of the microribbon‐based scaffold may be tuned by varying wet‐spinning rate, drying temperature, choice of drying agent, level of glutaraldehyde crosslinking, and microribbon density. When encapsulated in the microribbon‐based scaffold, human adipose‐derived stromal cells proliferated up to 30‐fold within 3 weeks. Furthermore, microribbons‐based scaffold demonstrate great flexibility and can sustain up to 90% strain and 3 MPa stress without failing. The unique mechanical properties of microribbon‐based scaffolds make them promising tools for engineering shock‐absorbing tissues such as cartilage and intervertebral discs.     

The Interaction of Laser and Photoconductor in a Continuous-Wave Terahertz Photomixer

The interaction of laser and photoconductor in an optical heterodyne conversion scheme is studied in detail. A dc biased photoconductor excited by two continuous-wave (CW) laser beams with a difference in their central frequencies falling in the terahertz spectrum is considered as the core element in all photoconductive photomixing structures. For this configuration the continuity equations for the electron and hole densities are solved in their general form along with the appropriate boundary conditions to find photocurrent distribution inside the photoconductor. It is shown that in a CW terahertz photomixing scheme the resulting photocurrent contains a dc component and a terahertz component. It is also shown that the amplitude and the phase of the terahertz component of the photocurrent are functions of the applied bias, physical parameters of the photoconductor, parameters of the lasers, and photomixer configuration. The dependency of the photocurrent on all of these parameters is explored in detail for a typical photomixer made of low-temperature-grown GaAs photoconductor.     

太赫兹技术发展及其应用于6G的挑战分析

作为6G潜在技术之一,太赫兹技术对数据速率提升、超密集连接、低时延传输等具有积极作用。首先阐述了太赫兹技术的传播特性和信道建模方法。根据传播特性确定了大尺度、小尺度和微尺度3个维度的太赫兹应用场景。接着,针对太赫兹特殊的频谱特性,设计了物理层波形、调制编码、超大规模多输入多输出(UM-MIMO),以及媒体接入控制(MAC)层波束管理方案。最后,关注了适用于太赫兹频段的智能超表面(RIS)技术,探讨了RIS关键使能技术与方案设计。     

Hardening silicon-on-insulator nMOSFETs by multiple-step Si+ implantation

A novel technique is proposed to improve total irradiation dose (TID) hardness of buried oxides in a 0.13 μm silicon-on-insulator (SOI) technology. Multiple-step Si ion implantation is implemented to avoid silicon film amorphization. Each implant step introduces silicon ion implantation of a lower dose into buried oxides which creates an amorphous/crystalline (a/c) interface inside the silicon layer. Rapid thermal annealing (RTA) removes implant-induced lattice damages by silicon recrystallization reflected in a/c interface moving towards the top silicon surface. The thermal process prevents top silicon layers from total amorphization arising in the technique of single high dose implantation method. X-ray Diffraction (XRD) spectrum confirms the existence of the a/c interface and determines the single implant dose. Experimental results on pseudo-MOS and H-gate partially-depleted SOI n-type MOSFETs show radiation tolerance up to 1.0 Mrad(Si) though introduced metastable electron traps lead to I–V hysteresis and bias instabilities.     

Terahertz emission upon the interband excitation of GaN layers

The experimental observation and study of terahertz photoluminescence upon the steady-state interband excitation of epitaxial n-GaN(Si) layers are reported. The properties of the terahertz emission spectrum and the dependence of the spectrum on temperature and photoexcitation intensity suggest that emission occurs due to the trapping of nonequilibrium electrons at charged donors. In the n-type material at low temperatures, charged donors can be formed as a result of the recombination of nonequilibrium holes with electrons localized at donor centers. The main contribution to terahertz photoluminescence is made by 2P ?? 1S optical transitions between the first excited state and ground state of the donors. In addition, optical transitions of electrons from the conduction band states to the ground state as well as to the excited states of donors are evident in the terahertz emission spectrum.