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The transmission enhancement of a THz pulse through an Ag/Ag_2 O layer detected by terahertz time-domain spectroscopy

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Chinese Physics B 2009年第7期18卷 2785-2787页

作者：陈华汪力 Department of Physics Southeast University Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Sciences

This paper reports a new way to detect the enhanced transmission of a THz electromagnetic wave through an Ag/Ag2O layer by THz-TDS （time-domain spectroscopy）. As the THz beam illuminates the sub-wavelength Ag particles gained by Ag2O thermal decomposition, the evanescent wave is generated. The evanescent wave is coupled by a 500μm-GaAs substrate, which attaches behind the Ag/Ag2O layer, and then it transmits to the far field to be detected. The experimental results indicate that the transmitting amplitude is enhanced, as well as the frequent shifting and spectra broadening.

关键词： terahertz time-domain spectroscopy Ag2O Ag evanescent wave frequent spectra

Far-infrared conductivity of CuS nanoparticles measured by terahertz time-domain spectroscopy

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Chinese Physics B 2010年第4期19卷 213-217页

作者：杨玉平张振伟施宇蕾冯帅王文忠 School of Science Minzu University of China Department of Physics Capital Normal University

This paper reports that terahertz time-domain spectroscopy is used to measure the optical properties of CuS nanoparticles in composite samples. The complex conductivity of pure CuS nanoparticles is extracted by applying the Bruggeman effective medium theory. The experimental data are consistent with the Drude-Smith model of conductivity in the range of 0.2 1.5 THz. The results demonstrate that carriers become localized with a backscattering behaviour in small-size nanostructures. In addition, the time constant for the carrier scattering is obtained and is only 64.3 fs due to increased electron interaction with interfaces and grain boundaries.

关键词： terahertz time-domain spectroscopy conductivity effective medium theory Drude-Smith model

Electronic properties of 2H-stacking bilayer MoS_(2)measured by terahertz time-domain spectroscopy

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Frontiers of physics 2023年第5期18卷 161-171页

作者： Xingjia Cheng Wen Xu Hua Wen Jing Zhang Heng Zhang Haowen Li Francois M.Peeters Qingqing Chen Key Laboratory of Materials Physics Institute of Solid State PhysicsHFIPSChinese Academy of SciencesHefei 230031China University of Science and Technology of China Hefei 230026China Micro Optical Instruments Inc. Shenzhen 518118China School of Physics and Astronomy and Yunnan Key Laboratory of Quantum Information of Yunnan Province Yunnan UniversityKunming 650091China Department of Physics University of AntwerpGroenenborgerlaan 171B-2020 AntwerpenBelgium

Bilayer (BL) molybdenum disulfide (MoS_(2)) is one of the most important electronic structures not only in valleytronics but also in realizing twistronic systems on the basis of the topological mosaics in moiré superlattices. In this work, BL MoS_(2) on sapphire substrate with 2H-stacking structure is fabricated. We apply the terahertz (THz) time-domain spectroscopy (TDS) for examining the basic optoelectronic properties of this kind of BL MoS_(2). The optical conductivity of BL MoS_(2) is obtained in temperature regime from 80 K to 280 K. Through fitting the experimental data with the theoretical formula, the key sample parameters of BL MoS_(2) can be determined, such as the electron density, the electronic relaxation time and the electronic localization factor. The temperature dependence of these parameters is examined and analyzed. We find that, similar to monolayer (ML) MoS_(2), BL MoS_(2) with 2H-stacking can respond strongly to THz radiation field and show semiconductor-like optoelectronic features. The theoretical calculations using density functional theory (DFT) can help us to further understand why the THz optoelectronic properties of BL MoS_(2) differ from those observed for ML MoS_(2). The results obtained from this study indicate that the THz TDS can be applied suitably to study the optoelectronic properties of BL MoS_(2) based twistronic systems for novel applications as optical and optoelectronic materials and devices.

关键词： terahertz time-domain spectroscopy bilayer MoS_(2) optoelectronics

terahertz time-domain spectroscopy and Its Applications

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Journal of Electronic Science and Technology 2014年第2期12卷 146-149页

作者： Guo-Zhong Zhao the Department of Physics Capital Normal University

The terahertz time-domain spectroscopy （THz-TDS） system and the related technology and the applications in Capital Normal University are presented. The most often used THz-TDS system as a spectroscopic measurement setup in our lab is introduced in detail, including the THz radiation source, the THz detection method and its measurement, and the control system. THz spectra of various materials is summarized and discussed. These materials include but not limited to two kinds of typical matter-the illegal drugs and explosives. The biological macro-molecules, cosmetics and fine chemical materials, edible pigments and food additives, homocysteic acid and related compounds, heavy ions in soil, Chinese medicines, tobacco and crops, oil and chemical products, carbon nanotubes, superconductors, and various semiconductors and their heterojunctions, are presented. THz emissions from the InAs and InN semiconductors surface are compared. THz spectral investigation of metallic mesh structures is summarized. Finally, an outlook of THz spectroscopic applications is given.

关键词： terahertz applications terahertz inspection terahertz spectrum terahertz time-domain spectroscopy

Research on Detection of Food additives Based on terahertz spectroscopy and Analytic Hierarchy Process

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Instrumentation 2024年第1期11卷 30-37页

作者： Miaoyu Zhao Fang Yan Wenwen Li Yangshuo Liu Inner Mongolia University of Science and Technology School of Automation and Electrical Engineering BaotouInner Mongolia 014010China

terahertz time-domain spectroscopy is a kind of far-infrared spectroscopy technology,and its spectrum reflects the internal properties of substances with rich physical and chemical information,so the use of terahertz waves can be used to qualitatively identify food additives containing nitrogen *** hierarchy process(AHP)was originally used to solve evaluation-type problems,and this paper introduces it into the field of terahertz spectral qualitative analysis,proposes a terahertz time-domain spectral qualitative identification method combined with analytic hierarchy process,and verifies the feasibility of the method by taking four common food additives(xylitol,L-alanine,sorbic acid,and benzoic acid)and two illegal additives(melamine,and Sudan Red No.I)as the objects of ***,the collected terahertz time-domain spectral data were pre-processed and transformed into a data set consisting of peaks,peak positions,peak numbers and overall trends;then,the data were divided into comparison and test sets,and a qualitative additive identification model incorporating analytic hierarchy process was constructed and parameter optimisation was *** results showed that the qualitative identification accuracies of additives based on single factors,i.e.,overall trend,peak value,peak position,and peak number,were 80.23%,70.93%,67.44%,and 40.70%,respectively,whereas the identification accuracy of the analytic hierarchy process qualitative identification method based on multi-factors could be improved to 92.44%.In addition,the fuzzy characterisation of the absorption spectrum data was binarised in the data pre-processing stage and used as the base data for the overall trend,and the recognition accuracy was improved to 94.19%by combining the fuzzy characterisation method of such data with the hierarchical analysis qualitative recognition *** results show that it is feasible to use terahertz technology to identify different varieties of additives,and th

关键词： terahertz time-domain spectroscopy analytic hierarchy process qualitative identification food additives

A new nonlinear photoconductive terahertz radiation source based on photon-activated charge domain quenched mode

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Chinese Physics B 2020年第7期29卷 147-150页

作者： Wei Shi Rujun Liu Chengang Dong Cheng Ma Key Laboratory of Ultrafast Photoelectric Technology and terahertz Science in Shaanxi Xi’an University of TechnologyXi’an 710048China

We present a high-performance terahertz(THz)radiation source based on the photon-activated charge domain(PACD)quenched mode of GaAs photoconductive antennas(GaAs PCA).The THz radiation characteristics of the GaAs PCA under different operating modes are *** with the linear mode,the intensity of THz wave radiated by the GaAs PCA can be greatly enhanced due to the avalanche multiplication effect of carriers in the PACD quenched *** results show that when the carrier multiplication ratio is 16.92,the peak-to-peak value of THz field radiated in the PACD quenched mode increases by as much as about 4.19 times compared to the maximum values in the linear mode.

关键词： photoconductive antenna terahertz time-domain spectroscopy photon-activated charge domain quenched mode

terahertz magnetic resonance in MnCr_(2)O_(4)under high magnetic field

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Chinese Physics B 2022年第10期31卷 534-538页

作者： Peng Zhang Kaibo He Zheng Wang Shile Zhang Jianming Dai Fuhai Su Department of Physics Laboratory of Functional Materials and Device for InformaticsFuyang Normal UniversityFuyang 236037China Anhui Provincial Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field LaboratoryHefei Institute of Physical Science(HFIPS)Chinese Academy of SciencesHefei 230031China Key Laboratory of Materials Physics Institute of Solid State PhysicsHFIPSChinese Academy of SciencesHefei 230031China

terahertz(THz)time-domain spectroscopy(THz-TDS)of polycrystalline MnCr_(2)O_(4)was performed at<9 T and low temperatures.A resonance absorption in the sub-THz range with linear blueshifts was observed as the magnetic field was increased from 4 T to 9 *** magnetism-driven absorptions originated from a ferromagnetic resonance,which agrees with low-field electron spin resonance measurements and ferromagnetic resonance *** low-temperature g-factors of MnCr_(2)O_(4)were also obtained using *** work provides new insights into the spin dynamics of chromite spinel compounds in the THz region.

关键词： chromium spinel terahertz time-domain spectroscopy ferromagnetic resonance

Substituent Effects on the Low-Frequency Vibrational Modes of Benzoic Acid and Related Compounds

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Chinese Journal of Chemistry 2007年第3期25卷 272-277页

作者：葛敏赵红卫王文锋余笑寒李文新 Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room temperature with terahertz time-domain spectroscopy （THz-TDS）. These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory （DFT） method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.

关键词： benzoic acid terahertz time-domain spectroscopy DP-T substituent effect

Temperature-dependent THz vibrational spectra of clenbuterol hydrochloride

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Science China(Physics,Mechanics & Astronomy) 2013年第4期56卷 713-717页

作者： YANG YuPing LEI XiangYun YUE Ai ZHANG ZhenWei School of Science Minzu University of China Beijing Key Laboratory for terahertz spectroscopy and Imaging Key Laboratory of Terahertz Optoelectronics (Ministry of Education) Department of Physics Capital Normal University

Using the high-resolution terahertz time-domain spectroscopy (THz-TDS) and the standard sample pellet technique, the far-infrared vibrational spectra of clenbuterol hydrochloride (CH), a 2 -adrenergic agonist for decreasing fat deposition and enhancing protein accretion, were measured in temperature range of 77-295 K. Between 0.2 and 3.6 THz (6.6-120.0 cm-1 ), seven highly resolved spectral features, strong line-narrowing and a frequency blue-shift were observed with cooling. However, ractopamine hydrochloride, with some structural and pharmacological similarities to clenbuterol hydrochloride, showed no spectral features, indicating high sensitivity and strong specificity of THz-TDS. These results could be used for the rapid and nondestructive CH residual detection in food safety control.

关键词： terahertz time-domain spectroscopy clenbuterol hydrochloride ractopamine hydrochloride