Journal articles: 'Terahertz'

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Guo, Yue, Shuqun Wu, Xuhui Liu, Lu Yang, and Chaohai Zhang. "The Application of Microplasma in the Terahertz Field: A Review." Applied Sciences 11, no. 24 (December 14, 2021): 11858. http://dx.doi.org/10.3390/app112411858.

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Terahertz functional devices are essential to the advanced applications of terahertz radiation in biology and medicine, nanomaterials, and wireless communications. Due to the small size and high plasma frequency of microplasma, the interaction between terahertz radiation and microplasma provides opportunities for developing functional terahertz devices based on microplasma. This paper reviews the applications of microplasma in terahertz sources, terahertz amplifiers, terahertz filters, and terahertz detectors. The prospects and challenges of the interdisciplinary research between microplasma and terahertz technology are discussed.

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Yao, Shutong, and Junyi Teng. "Terahertz communication for 6G networks: Opportunities and challenges." Applied and Computational Engineering 46, no. 1 (March 15, 2024): 232–41. http://dx.doi.org/10.54254/2755-2721/46/20241431.

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This paper introduces terahertz communication technology, the core component of future 6 g wireless communication. Terahertz band communication can expand the spectrum range of communication, increase its capacity limit, and can be effectively utilized and realized in many fields. This paper systematically describes the background, development, difficulties and challenges of terahertz communication, as well as the possible application fields and development prospects in the future, and introduces in detail the key technologies of terahertz communication, including the simulation processing of terahertz signal processing and modulation technology and the research data of the system. In this paper, I use the ten-ray model modeling to help me understand the propagation characteristics of terahertz waves in different environments, and provide reference and guidance for the application of terahertz waves and system design. Finally, the future application field of terahertz are expanded and prospected. It describes new and predictable technologies that combine the power of terahertz technology with other technologies, such as exploring hybrid terahertz/optical wireless links, terahertz automotive applications, terahertz communications to enhance data center performance and terahertz 3D beamforming technology.

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Wang, Chen, Jianyuan Qin, Wendao Xu, Min Chen, Lijuan Xie, and Yibin Ying. "Terahertz Imaging Applications in Agriculture and Food Engineering: A Review." Transactions of the ASABE 61, no. 2 (2018): 411–24. http://dx.doi.org/10.13031/trans.12201.

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Abstract. Terahertz technology, including terahertz spectroscopy and terahertz imaging, is gaining increasing attention and plays an important role in various fields. With the development of terahertz sources and detectors in recent decades, terahertz imaging has been applied in many fields, including security screening, material evaluation, biomedicine, agriculture, and food science. However, progress has been comparatively slow in applying terahertz imaging to agriculture and food engineering. In this article, some commonly used terahertz imaging systems are summarized, and various applications of terahertz imaging in agriculture and food engineering are reviewed, including food safety and quality inspection, seed inspection, water content evaluation of plant leaves, and others. Challenges and the future outlook of terahertz imaging are also discussed. Keywords: Agriculture, Food, Instrumentation, Seed, Terahertz imaging.

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Okada, Kosuke, Quentin Cassar, Hironaru Murakami, Gaëtan MacGrogan, Jean-Paul Guillet, Patrick Mounaix, Masayoshi Tonouchi, and Kazunori Serita. "Label-Free Observation of Micrometric Inhomogeneity of Human Breast Cancer Cell Density Using Terahertz Near-Field Microscopy." Photonics 8, no. 5 (May 1, 2021): 151. http://dx.doi.org/10.3390/photonics8050151.

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Terahertz-light imaging is attracting great attention as a new approach in non-invasive/non-staining biopsy of cancerous tissues. Positively, terahertz light has been shown to be sensitive to the cell density, the hydration content, and the chemical composition of biological samples. However, the spatial resolution of terahertz imaging is typically limited to several millimeters, making it difficult to apply the technology to image biological tissues which have sub-terahertz-wavelength-scale inhomogeneity. For overcoming the resolution, we have recently developed a terahertz near-field microscope with a spatial resolution of 10 µm, named scanning point terahertz source (SPoTS) microscope. In contrast to conventional far-field terahertz techniques, this microscope features the near-field interactions between samples and point terahertz sources on a sub-terahertz-wavelength scale. Herein, to evaluate the usefulness of terahertz imaging in cancer tissue biopsy in greater detail, we performed terahertz near-field imaging of a paraffin-embedded human-breast-cancer section having sub-terahertz-wavelength-scale inhomogeneity of the cancer cell density using the SPoTS microscope. The observed terahertz images successfully visualized local (~250 µm) inhomogeneities of the cell density in breast invasive ductal carcinoma. These results may bypass the terahertz limitation in terms of spatial resolution and may further motivate the application of terahertz light to cancer tissue biopsy.

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Keiser, George, and Pernille Klarskov. "Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging." Photonics 6, no. 1 (February 28, 2019): 22. http://dx.doi.org/10.3390/photonics6010022.

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This article reviews recent advances in terahertz science and technology that rely on confining the energy of incident terahertz radiation to small, very sub-wavelength sized regions. We focus on two broad areas of application for such field confinement: metamaterial-based nonlinear terahertz devices and terahertz near-field microscopy and spectroscopy techniques. In particular, we focus on field confinement in: terahertz nonlinear absorbers, metamaterial enhanced nonlinear terahertz spectroscopy, and in sub-wavelength terahertz imaging systems.

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Vertiy, Alexey A., Harun Cetinkaya, and Mustafa Tekbas. "Subsurface Sub-terahertz and Terahertz Tomography." PIERS Online 6, no. 5 (2010): 485–89. http://dx.doi.org/10.2529/piers091208093425.

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Du, Wanyi, Yuanyuan Huang, Yixuan Zhou, and Xinlong Xu. "Terahertz interface physics: from terahertz wave propagation to terahertz wave generation." Journal of Physics D: Applied Physics 55, no. 22 (February 4, 2022): 223002. http://dx.doi.org/10.1088/1361-6463/ac3f58.

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Abstract Terahertz (THz) interface physics as a new interdiscipline between the THz technique and condensed matter physics has undergone rapid development in recent years. In particular, the development of advanced materials, such as graphene, transitional metal dichalcogenides, topological insulators, ferromagnetic metals, and metamaterials, has revolutionized the interface field and further promoted the development of THz functional devices based on interface physics. Moreover, playing at the interface of these advanced materials could unveil a wealth of fascinating physical effects such as charge transfer, proximity effect, inverse spin-Hall effect, and Rashba effect with THz technology by engineering the charge, spin, orbit, valley, and lattice degrees of freedom. In this review, we start with a discussion of the basic theory of THz interface physics, including interface formation with advanced materials, THz wave reflection and transmission at the interface, and band alignment and charge dynamics at the interface. Then we move to recent progress in advanced materials from THz wave propagation to THz wave generation at the interface. In THz wave propagation, we focus on THz wave impedance-matching, Goos–Hänchen and Imbert–Fedorov shifts in THz region, interfacial modulation and interfacial sensing based on THz waves. In THz wave generation, we summarize ongoing coherent THz wave generation from van der Waals interfaces, multiferroic interfaces, and magnetic interfaces. The fascinating THz interface physics of advanced materials is promising and promotes novel THz functional devices for manipulating propagation and generation of THz waves at interfaces.

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Ma, Shaoqing, Peng Ding, Zhengxuan Zhou, Huilong Jin, Xiaoli Li, and Yingwei Li. "Terahertz Radiation Modulates Neuronal Morphology and Dynamics Properties." Brain Sciences 14, no. 3 (March 14, 2024): 279. http://dx.doi.org/10.3390/brainsci14030279.

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Terahertz radiation falls within the spectrum of hydrogen bonding, molecular rotation, and vibration, as well as van der Waals forces, indicating that many biological macromolecules exhibit a strong absorption and resonance in this frequency band. Research has shown that the terahertz radiation of specific frequencies and energies can mediate changes in cellular morphology and function by exciting nonlinear resonance effects in proteins. However, current studies have mainly focused on the cellular level and lack systematic studies on multiple levels. Moreover, the mechanism and law of interaction between terahertz radiation and neurons are still unclear. Therefore, this paper analyzes the mechanisms by which terahertz radiation modulates the nervous system, and it analyzes and discusses the methods by which terahertz radiation modulates neurons. In addition, this paper reviews the laws of terahertz radiation’s influence on neuronal morphology and kinetic properties and discusses them in detail in terms of terahertz radiation frequency, energy, and time. In the future, the safety of the terahertz radiation system should be considered first to construct the safety criterion of terahertz modulation, and the spatial resolution of the terahertz radiation system should be improved. In addition, the systematic improvement of the laws and mechanisms of terahertz modulation of the nervous system on multiple levels is the key to applying terahertz waves to neuroscience. This paper can provide a platform for researchers to understand the mechanism of the terahertz–nervous system interaction, its current status, and future research directions.

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Gao, Feilong, Mingzhe Jiang, and Shaodong Hou. "A Chirped Characteristic-Tunable Terahertz Source for Terahertz Sensing." Sensors 24, no. 16 (August 22, 2024): 5419. http://dx.doi.org/10.3390/s24165419.

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In broadband terahertz waves generated by femtosecond lasers, spatial chirp will be simultaneously produced with the introduction of angular dispersion. The chirp characteristics of the terahertz wave will directly affect the frequency response, bandwidth response, and intensity response of the terahertz sensor. To enhance the capability of terahertz sensors, it is necessary to control and improve the chirped characteristics of broadband terahertz sources. We generate a chirped terahertz wave via optical rectification in a LiNbO3 prism using the technique of pulse front tilt. The effect of the pump-beam spot size on THz generation is systematically studied. The pump’s spot size is manipulated using a telescope system. With a pump spot diameter of 1.8 mm, the scanning spectrum of the THz pulse is narrower and is divided into multiple distinct peaks. In contrast, using a pump spot diameter of 3.7 mm leads to increased efficiency in the generation of THz pulses. Also, we investigate the underlying properties governing the generation of chirped terahertz pulses using varying pump pulse spot diameters.

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Liu, Jianlong, Xin Li, Ruirui Jiang, Kaiqiang Yang, Jing Zhao, Sayed Ali Khan, Jiancheng He, Peizhong Liu, Jinfeng Zhu, and Baoqing Zeng. "Recent Progress in the Development of Graphene Detector for Terahertz Detection." Sensors 21, no. 15 (July 22, 2021): 4987. http://dx.doi.org/10.3390/s21154987.

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Terahertz waves are expected to be used in next-generation communications, detection, and other fields due to their unique characteristics. As a basic part of the terahertz application system, the terahertz detector plays a key role in terahertz technology. Due to the two-dimensional structure, graphene has unique characteristics features, such as exceptionally high electron mobility, zero band-gap, and frequency-independent spectral absorption, particularly in the terahertz region, making it a suitable material for terahertz detectors. In this review, the recent progress of graphene terahertz detectors related to photovoltaic effect (PV), photothermoelectric effect (PTE), bolometric effect, and plasma wave resonance are introduced and discussed.

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JIN, Y. H., and X. C. ZHANG. "TERAHERTZ OPTICAL RECTIFICATION." Journal of Nonlinear Optical Physics & Materials 04, no. 02 (April 1995): 459–95. http://dx.doi.org/10.1142/s0218863595000185.

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We present experimental measurements of Terahertz optical rectification in electro-optic crystals. The measured data was compared with a simple theoretical analysis (anharmonic oscillator model). We also measured Terahertz-bandwidth subpicosecond electromagnetic radiation via nearly-degenerate difference-frequency generation in electrooptic materials. The variation in Terahertz emission with crystal orientation demonstrated that the generation of Terahertz radiation via optical rectification involves a bulk second-order nonlinear process. We studied Terahertz optical rectification from zincblende crystals as the incident photon energy was tuned across the semiconductor optical absorption band-edge (resonant excitation). We also present the measurement of temperature-dependent Terahertz optical rectification. A comparison between the two second-order nonlinear processes, sum-frequency generation (second-harmonic generation) and different-frequency generation (optical rectification) is presented.

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Ge, Hongyi, Zhenyu Sun, Yuying Jiang, Xuyang Wu, Zhiyuan Jia, Guangyuan Cui, and Yuan Zhang. "Recent Advances in THz Detection of Water." International Journal of Molecular Sciences 24, no. 13 (June 30, 2023): 10936. http://dx.doi.org/10.3390/ijms241310936.

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The frequency range of terahertz waves (THz waves) is between 0.1 and 10 THz and they have properties such as low energy, penetration, transients, and spectral fingerprints, which are especially sensitive to water. Terahertz, as a frontier technology, have great potential in interpreting the structure of water molecules and detecting biological water conditions, and the use of terahertz technology for water detection is currently frontier research, which is of great significance. Firstly, this paper introduces the theory of terahertz technology and summarizes the current terahertz systems used for water detection. Secondly, an overview of theoretical approaches, such as the relaxation model and effective medium theory related to water detection, the relationship between water molecular networks and terahertz spectra, and the research progress of the terahertz detection of water content and water distribution visualization, are elaborated. Finally, the challenge and outlook of applications related to the terahertz wave detection of water are discussed. The purpose of this paper is to explore the research domains on water and its related applications using terahertz technology, as well as provide a reference for innovative applications of terahertz technology in moisture detection.

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Lyu, Nanfang, Jian Zuo, Yuanmeng Zhao, and Cunlin Zhang. "Terahertz Synthetic Aperture Imaging with a Light Field Imaging System." Electronics 9, no. 5 (May 18, 2020): 830. http://dx.doi.org/10.3390/electronics9050830.

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In terahertz imaging systems based on Gaussian beam active illumination and focal plane array detectors, severe image distortion has been observed, which significantly reduces the resolving power of the imaging system. To solve this problem, a novel computational method, Light Field Imaging (LFI), has been introduced for terahertz imaging. A conventional transmission-type terahertz imaging system based on a gas-pumped terahertz source and terahertz Focal Plane Array Detectors (FPA) arrays is established to analyze the problem of image distortion. An experimental virtual camera array terahertz LFI system is also established. With the acquisition and reconstruction of synthetic aperture terahertz light fields, the improvement on resolving power and SNR performance have been validated.

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hevchik-Shekera, A. "Design of optical components for terahertz/sub-terahertz imaging systems." Semiconductor Physics Quantum Electronics and Optoelectronics 18, no. 3 (September 30, 2015): 341–43. http://dx.doi.org/10.15407/spqeo18.03.341.

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Zhu, Hailiang, Kai Wang, Ganyu Liu, Gengchen Wang, Jinchao Mou, Weiwei Zhang, and Gao Wei. "A Terahertz Optomechanical Detector Based on Metasurface and Bi-Material Micro-Cantilevers." Micromachines 13, no. 5 (May 21, 2022): 805. http://dx.doi.org/10.3390/mi13050805.

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Terahertz imaging technology has shown great potential in many fields. As the core component of terahertz imaging systems, terahertz detectors have received extensive attention. In this paper, a metasurface-based terahertz optomechanical detector is proposed, which is made of two fabrication-friendly materials: gold and silicon nitride. The optomechanical detector is essentially a thermal detector composed of metasurface absorber, bi-material micro-cantilevers and heat insulation pillars. Compared with traditional thermal terahertz detectors, the optomechanical detector employs a metasurface absorber as the terahertz radiation coupler and obtains an absorptivity higher than 90% from 3.24 to 3.98 THz, which is much higher than that of traditional terahertz detectors with absorbers made from natural materials. Furthermore, the detector is fabricated by MEMS process and its responsivity has been verified by a specifically designed optical read-out system; the measured optomechanical responsivity is 24.8 μm/μW, which agrees well with the multi-physics simulation. These results indicated that the detector can be employed as a pixel to form a terahertz focal plane array in the future, and further realize real-time terahertz imaging at room temperature.

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Yang, Peidi, Baolong Zhang, Jinglong Ma, Yutong Li, Jungang Miao, and Xiaojun Wu. "Nonlinear terahertz effects of gold nanofilms." Terahertz Science and Technology 14, no. 1 (March 2021): 20–30. http://dx.doi.org/10.1051/tst/2021141020.

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Nonlinear interaction between strong-field terahertz electromagnetic waves and matters will become one of the next hot research frontiers in nonlinear optics. However, the lack of strong terahertz radiation sources and appropriate nonlinear terahertz materials have impeded its progress. Here we systematically have investigated the strong-field terahertz nonlinear effects of gold (Au) nanofilms on different substrates, including SiO2, high-resistivity Si and SiO2-high-resistivity Si hybrid substrates. The strong-field terahertz waves are emitted from lithium niobate crystals via tilted pulse front technique, and obvious nonlinear transmission responses are observed along with varying the incident field strengths for all the Au samples on the three types of the substrates. The nonlinear behavior is enhanced when the gold nanofilm thickness increases, which can be qualitatively understood by introducing the quantum tunneling effect and carrier multiplication theory generated at the Au nano-slits under the illumination of the strong-field terahertz pulses. Our demonstrations not only open a new paradigm for nonlinear terahertz investigations and future high-speed terahertz devices, but also provide an effective platform for exploring extreme terahertz sciences.

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Yu, Hongguan, Huacai Wang, Qiguang Wang, Shijun Ge, and Wei Hu. "Liquid Crystal-Tuned Planar Optics in Terahertz Range." Applied Sciences 13, no. 3 (January 21, 2023): 1428. http://dx.doi.org/10.3390/app13031428.

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Recently, terahertz waves of higher frequencies compared to microwave and radio frequency have shown great potential in radar detection and high-speed wireless communication. To spatially control the wavefront of terahertz beams, various novel components, such as terahertz filters, polarization converters and lenses, have been investigated. Metamaterials and metasurfaces have become the most promising technique for the free manipulation of terahertz waves. Metadevices integrated with liquid crystals have been widely used in active terahertz devices. In this review, the birefringence of liquid crystals in the terahertz band and terahertz devices based on liquid crystals are summarized. By integrating liquid crystals with plasmonic metamaterials, the functions become dynamically adjustable and are reconstructed. Utilizing liquid crystals to change the resonance of metamaterials, tunable filters, absorbers, and programmable metasurfaces are realized. To solve the problem of low efficiency, terahertz wavefront shaping devices based on dielectric metasurfaces and liquid crystals, such as a variable deflection angle grating and zoom metalenses, are presented. Finally, we discuss and anticipate the future developments of liquid-crystal-integrated meta-devices, which will inspire broad applications in terahertz communication and imaging.

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Katayama, Ikufumi, Hiroki Kawakami, Kotaro Araki, Yusuke Arashida, Yasuo Minami, Lie-Wei Nien, Orjan Sele Handegard, Tadaaki Nagao, Masahiro Kitajima, and Jun Takeda. "Ultrafast carrier generation in Bi1-xSbx thin films induced by intense monocycle terahertz pulses." EPJ Web of Conferences 205 (2019): 04016. http://dx.doi.org/10.1051/epjconf/201920504016.

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Using terahertz-pump and terahertz-probe spectroscopy, we investigated terahertz-induced carrier generation processes in Bi1-xSbx thin films. The field dependence of the terahertz-induced transmittance change indicates distinct nonlinearity related to the Zener tunneling in narrow band-gap materials.

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Wang, Yue, Zi-Jian Cui, Xiao-Ju Zhang, Da-Chi Zhang, Xiang Zhang, Tao Zhou, and Xuan Wang. "Research progress of metamaterials powered advanced terahertz biochemical sensing detection techniques." Acta Physica Sinica 70, no. 24 (2021): 247802. http://dx.doi.org/10.7498/aps.70.20211752.

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The electromagnetic wave in the terahertz region shows many promising properties, such as non-ionizing, sensitivity to weak resonance, and gradually becomes a basic and applied research hotspot of physics, information, materials, biology, chemistry and other disciplines. However, the analyte molecules tend to be of subwavelength size, and cannot have sufficient interaction with the incident terahertz wave. Small disturbances and subtle features are difficult to detect, which undoubtedly hinders the further development of the terahertz biochemical sensing and detection. The rapid development of terahertz metamaterials provides an alternative method to overcome this obstacle. The intense electromagnetic field enhancement induced by metamaterials allows the sensing and detection application to surpass the limitation of classical terahertz spectroscopy, which is due to the enhancement of the interaction between the analyte and terahertz. In recent years, a series of researches based on terahertz metamaterials combined with new materials, new structures and new mechanisms has offered new opportunities for the application of highly sensitive terahertz biochemical sensing and detection. In this paper, the recent advances in the application of terahertz metamaterials biochemical sensing are reviewed. The related concepts are briefly introduced and the influences of different factors on the sensing performance of metamaterial sensor are analyzed. According to the material selection and design strategies, the related researches of terahertz metamaterial biochemical sensing and detection are summarized. Furthermore, the novel strategy of terahertz metamaterial sensing and detection application based on multidisciplinary are presented, and the future development directions are also discussed, which will greatly conduce to expanding the practicality of terahertz sensing and detection.

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Seifert, Tom S., Liang Cheng, Zhengxing Wei, Tobias Kampfrath, and Jingbo Qi. "Spintronic sources of ultrashort terahertz electromagnetic pulses." Applied Physics Letters 120, no. 18 (May 2, 2022): 180401. http://dx.doi.org/10.1063/5.0080357.

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Spintronic terahertz emitters are broadband and efficient sources of terahertz radiation, which emerged at the intersection of ultrafast spintronics and terahertz photonics. They are based on efficient spin-current generation, spin-to-charge-current conversion, and current-to-field conversion at terahertz rates. In this Editorial, we review the recent developments and applications, the current understanding of the physical processes, and the future challenges and perspectives of broadband spintronic terahertz emitters.

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Liu, Shuxiang, Li Deng, Meijun Qu, and Shufang Li. "Polarization-Independent Tunable Ultra-Wideband Meta-Absorber in Terahertz Regime." Electronics 8, no. 8 (July 26, 2019): 831. http://dx.doi.org/10.3390/electronics8080831.

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In this paper, we demonstrate an ultra-broadband terahertz bilayer graphene-based absorption structure. It has two stacking graphene layers sandwiched by an Au cylinders array, backed by a metallic ground plane. Au cylinders are used to adjust the input impedance to be closely matched to the free space, enabling an ultra-broadband absorption. The absorption spectrum of the bilayer graphene-based absorption structure with Au cylinder arrays shows a bandwidth of 7.1 THz, with the absorption exceeding 80%. The achieved ultra-wideband THz meta-absorber has high absorption, independence of polarization property, simultaneously, illustrating to be a promising candidate for teraherz broadband absorption application.

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Pu, Zhengping, Yu Wu, Zhongjie Zhu, Hongwei Zhao, and Donghong Cui. "A new horizon for neuroscience: terahertz biotechnology in brain research." Neural Regeneration Research 20, no. 2 (March 1, 2024): 309–25. http://dx.doi.org/10.4103/nrr.nrr-d-23-00872.

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Terahertz biotechnology has been increasingly applied in various biomedical fields and has especially shown great potential for application in brain sciences. In this article, we review the development of terahertz biotechnology and its applications in the field of neuropsychiatry. Available evidence indicates promising prospects for the use of terahertz spectroscopy and terahertz imaging techniques in the diagnosis of amyloid disease, cerebrovascular disease, glioma, psychiatric disease, traumatic brain injury, and myelin deficit. In vitro and animal experiments have also demonstrated the potential therapeutic value of terahertz technology in some neuropsychiatric diseases. Although the precise underlying mechanism of the interactions between terahertz electromagnetic waves and the biosystem is not yet fully understood, the research progress in this field shows great potential for biomedical noninvasive diagnostic and therapeutic applications. However, the biosafety of terahertz radiation requires further exploration regarding its two-sided efficacy in practical applications. This review demonstrates that terahertz biotechnology has the potential to be a promising method in the field of neuropsychiatry based on its unique advantages.

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Zhang, Weili, Abul K. Azad, and Jiaguang Han. "Resonant Excitation of Terahertz Surface Plasmons in Subwavelength Metal Holes." Active and Passive Electronic Components 2007 (2007): 1–8. http://dx.doi.org/10.1155/2007/40249.

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We present a review of experimental studies of resonant excitation of terahertz surface plasmons in two-dimensional arrays of subwavelength metal holes. Resonant transmission efficiency higher than unity was recently achieved when normalized to the area occupied by the holes. The effects of hole shape, hole dimensions, dielectric function of metals, polarization dependence, and array film thickness on resonant terahertz transmission in metal arrays were investigated by the state-of-the-art terahertz time-domain spectroscopy. In particular, extraordinary terahertz transmission was demonstrated in arrays of subwavelength holes made even from Pb, a generally poor metal, and having thickness of only one-third of skin depth. Terahertz surface plasmons have potential applications in terahertz imaging, biosensing, interconnects, and development of integrated plasmonic components for terahertz generation and detection.

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Wang, Jianfeng, Xuelei Sui, Wenhui Duan, Feng Liu, and Bing Huang. "Density-independent plasmons for terahertz-stable topological metamaterials." Proceedings of the National Academy of Sciences 118, no. 19 (May 5, 2021): e2023029118. http://dx.doi.org/10.1073/pnas.2023029118.

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To efficiently integrate cutting-edge terahertz technology into compact devices, the highly confined terahertz plasmons are attracting intensive attention. Compared to plasmons at visible frequencies in metals, terahertz plasmons, typically in lightly doped semiconductors or graphene, are sensitive to carrier density (n) and thus have an easy tunability, which leads to unstable or imprecise terahertz spectra. By deriving a simplified but universal form of plasmon frequencies, here, we reveal a unified mechanism for generating unusual n-independent plasmons (DIPs) in all topological states with different dimensions. Remarkably, we predict that terahertz DIPs can be excited in a two-dimensional nodal line and one-dimensional nodal point systems, confirmed by the first-principle calculations on almost all existing topological semimetals with diverse lattice symmetries. Besides n-independence, the feature of Fermi velocity and degeneracy factor dependencies in DIPs can be applied to design topological superlattice and multiwalled carbon nanotube metamaterials for broadband terahertz spectroscopy and quantized terahertz plasmons, respectively. Surprisingly, high spatial confinement and quality factor, also insensitive to n, can be simultaneously achieved in these terahertz DIPs. Our findings pave the way for developing topological plasmonic devices for stable terahertz applications.

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Zeng, Hongxin, Sen Gong, Lan Wang, Tianchi Zhou, Yaxin Zhang, Feng Lan, Xuan Cong, et al. "A review of terahertz phase modulation from free space to guided wave integrated devices." Nanophotonics 11, no. 3 (December 19, 2021): 415–37. http://dx.doi.org/10.1515/nanoph-2021-0623.

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Abstract In the past ten years, terahertz technology has developed rapidly in wireless communications, spectroscopy, and imaging. Various functional devices have been developed, such as filters, absorbers, polarizers, mixers, and modulators. Among these, the terahertz phase modulation is a current research hotspot. It is the core technology to realize flexible control of the terahertz wavefront, beam scanning, focusing deflection. It is indispensable in terahertz wireless communication, high-resolution imaging, and radar systems. This review summarizes the research progress of terahertz phase modulators from the two major types: free space and guided wave integration. Among these, the free space terahertz phase modulator is realized by combining the tunable materials and artificial metasurfaces. Based on different types of tunable materials, the terahertz free space phase modulator combining the semiconductor, liquid crystal, phase change materials, graphene, and other two-dimensional materials are introduced, and the influence of different materials on the phase modulation performance is discussed and analyzed. The monolithic integration and waveguide embedding methods are introduced separately, and the characteristics of different forms of terahertz-guided wave phase modulation are also discussed. Finally, the development trends of terahertz phase modulators, possible new methods, and future application requirements are discussed.

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Yao, Shutong, and Wutong Lei. "Design and review of terahertz antennas." Applied and Computational Engineering 73, no. 1 (July 5, 2024): 280–87. http://dx.doi.org/10.54254/2755-2721/73/20240412.

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With the rapid development of wireless cellular communication from 1G to 5G, it is about to enter the 6g era, not only are people more connected, but more and more smart devices have also realized the Internet, and this trend will continue until 2030 and beyond, when everything will be smart Internet anytime, anywhere. If smart devices can sense their surroundings and share environmental information with other smart devices, then this connection will become more intelligent. This paper introduces the core technology of future 6g wireless communication, the terahertz antenna in the equipment part of terahertz communication, and carries on the design of a new terahertz antenna, which is mainly used for transmitting and receiving terahertz signals, and can effectively convert electromagnetic wave energy into wireless signals to realize wireless communication with other devices. The design and performance of terahertz antennas directly affect the transmission efficiency and reliability of terahertz communication systems. In addition, the role of the new terahertz antenna model can expand the application field of terahertz technology and promote the wide application of terahertz technology in communication, security, medical and measurement fields.

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PICKWELL-MACPHERSON, EMMA, SHENGYANG HUANG, KANIS WAI CHI KAN, YIWEN SUN, and YUAN TING ZHANG. "RECENT DEVELOPMENTS OF TERAHERTZ TECHNOLOGY IN BIOMEDICINE." Journal of Innovative Optical Health Sciences 01, no. 01 (June 2008): 29–44. http://dx.doi.org/10.1142/s1793545808000042.

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Terahertz technology is continually evolving and much progress has been made in recent years. Many new applications are being discovered and new ways to implement terahertz imaging investigated. In this review, we limit our discussion to biomedical applications of terahertz imaging such as cancer detection, genetic sensing and molecular spectroscopy. Our discussion of the development of new terahertz techniques is also focused on those that may accelerate the progress of terahertz imaging and spectroscopy in biomedicine.

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Sun, Xu, Zhi-Hui Lyu, Hai-Zhong Wu, Cong-Sen Meng, Dong-Wen Zhang, Zhi-Zhong Lu, Xiao-Wei Wang, Zeng-Xiu Zhao, and Jian-Min Yuan. "Broadband Terahertz Detection by Laser Plasma with Balanced Optical Bias." Sensors 22, no. 19 (October 6, 2022): 7569. http://dx.doi.org/10.3390/s22197569.

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Using a controlled optical bias and balanced geometry, we propose a new scheme for broadband terahertz detection by laser-gas interaction without high-voltage manipulation. Compared to the conventional optical bias scheme, the common noise is reduced and the dynamic range as well as the signal-to-noise ratio are doubled. It provides a simple alternative for coherent broadband terahertz detection. The influence of optical bias on terahertz waveform is also investigated, and the evolution of the terahertz-induced second harmonic with probe delay is further revealed. This new detection scheme for broadband terahertz will boost the application of terahertz time-domain spectroscopy for its miniaturization and integrability.

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Watanabe, Shinichi. "Terahertz Polarization Imaging and Its Applications." Photonics 5, no. 4 (December 12, 2018): 58. http://dx.doi.org/10.3390/photonics5040058.

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This review focuses on several recent research activities regarding precise and fast polarization-sensitive terahertz time-domain spectroscopy systems for imaging purposes, and explains three interesting application examples. Owing to modulation techniques that have recently been developed for the evaluation of the instantaneous terahertz electric-field (E-field) vector, fast and precise terahertz polarization imaging becomes feasible. This terahertz technology enables high-resolution surface topography, precise understanding of the spatial E-field vector distribution of the focused terahertz pulse, and examination of strain-induced birefringence in polymeric materials. These examples constitute a new application area of terahertz photonics with emphasis on both fundamental optics and industrial applications.

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Wu, Yu Deng, and Guang Jun Ren. "Study of Enhanced Surface Raman Scattering on Nano-Particle in Terahertz Range." Advanced Materials Research 977 (June 2014): 108–11. http://dx.doi.org/10.4028/www.scientific.net/amr.977.108.

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Researched the surface-enhanced Raman scattering on nanoparticle in terahertz range, and proved the existence of the same phenomenon-Raman enhancements in the terahertz band. By studying the electromagnetic enhancement principle of surface-enhanced Raman scattering, proposed to using finite difference time-domain to simulate the surface-enhanced Raman scattering of nanoparticles in the terahertz irradiated. Simulation results show that the FDTD method can effectively simulate the scattering of nanoparticles in terahertz band, resulting in surface-enhanced Raman scattering from the visible and infrared bands extended to the terahertz band, and the result provides basis for terahertz waves and surface-enhanced Raman scattering the combined application.

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Hofmann, T., C. M. Herzinger, J. L. Tedesco, D. K. Gaskill, J. A. Woollam, and M. Schubert. "Terahertz ellipsometry and terahertz optical-Hall effect." Thin Solid Films 519, no. 9 (February 2011): 2593–600. http://dx.doi.org/10.1016/j.tsf.2010.11.069.

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Finneran, Ian A., Ralph Welsch, Marco A. Allodi, Thomas F. Miller, and Geoffrey A. Blake. "Coherent two-dimensional terahertz-terahertz-Raman spectroscopy." Proceedings of the National Academy of Sciences 113, no. 25 (June 6, 2016): 6857–61. http://dx.doi.org/10.1073/pnas.1605631113.

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We present 2D terahertz-terahertz-Raman (2D TTR) spectroscopy, the first technique, to our knowledge, to interrogate a liquid with multiple pulses of terahertz (THz) light. This hybrid approach isolates nonlinear signatures in isotropic media, and is sensitive to the coupling and anharmonicity of thermally activated THz modes that play a central role in liquid-phase chemistry. Specifically, by varying the timing between two intense THz pulses, we control the orientational alignment of molecules in a liquid, and nonlinearly excite vibrational coherences. A comparison of experimental and simulated 2D TTR spectra of bromoform (CHBr3), carbon tetrachloride (CCl4), and dibromodichloromethane (CBr2Cl2) shows previously unobserved off-diagonal anharmonic coupling between thermally populated vibrational modes.

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Yano, Kaori, and Toshiaki Hattori. "Improving a Terahertz Time-Domain Spectroscopy Apparatus Using Neodymium Magnets." International Letters of Chemistry, Physics and Astronomy 62 (November 2015): 10–14. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.62.10.

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The signal-to-noise ratio obtained from terahertz time-domain spectroscopy is significantly affected by the low available power of terahertz waves. We constructed a terahertz-wave source with emission power enhanced by a magnetic field. The emitter is composed of an InAs wafer and two neodymium magnets. The emitter was irradiated by femtosecond laser pulses. The data quality of terahertz spectroscopic measurements was evaluated, and reduction of error in the data obtained due to the terahertz power enhancement was observed.

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Yano, Kaori, and Toshiaki Hattori. "Improving a Terahertz Time-Domain Spectroscopy Apparatus Using Neodymium Magnets." International Letters of Chemistry, Physics and Astronomy 62 (November 27, 2015): 10–14. http://dx.doi.org/10.56431/p-cw453x.

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The signal-to-noise ratio obtained from terahertz time-domain spectroscopy is significantly affected by the low available power of terahertz waves. We constructed a terahertz-wave source with emission power enhanced by a magnetic field. The emitter is composed of an InAs wafer and two neodymium magnets. The emitter was irradiated by femtosecond laser pulses. The data quality of terahertz spectroscopic measurements was evaluated, and reduction of error in the data obtained due to the terahertz power enhancement was observed.

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Rumiantsev, B. V., A. V. Pushkin, D. Z. Suleimanova, N. A. Zhidovtsev, and F. V. Potemkin. "Generation of Intense Few-Cycle Terahertz Radiation in Organic Crystals Pumped by 1.24-μm Multigigawatt Chirped Laser Pulses." JETP Letters 117, no. 8 (April 2023): 566–73. http://dx.doi.org/10.1134/s0021364023600416.

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It has been shown that the spectrum of intense few-cycle terahertz radiation generated in a DAST organic crystal can be controlled by chirping 1.24-μm pump femtosecond laser radiation of a chromium forsterite laser system. It has been found that an increase in the linear chirp of generating radiation results in the narrowing of the spectrum of terahertz radiation and its redshift. The simulation of the generation of terahertz radiation within the model of three-wave mixing has shown that this effect is due to a change in the phase matching width of the degenerate generation of the difference frequency of terahertz range. In addition, the comparative analysis of terahertz radiation spectra generated in DAST, DSTMS, OH1, and BNA organic crystals indicates that the spectral–temporal properties of terahertz radiation can be more roughly controlled by choosing an appropriate crystal. The proposed approach to control the terahertz radiation spectrum by chirping the pump pulse provides the foundation for spectroscopic studies using intense terahertz radiation with controlled spectral–temporal properties.

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OTSUJI, TAIICHI, TAKUYA NISHIMURA, YUKI TSUDA, YAHYA MOUBARAK MEZIANI, TETSUYA SUEMITSU, and EIICHI SANO. "EMISSION AND INTENSITY MODULATION OF TERAHERTZ ELECTROMAGNETIC RADIATION UTILIZING 2-DIMENSIONAL PLASMONS IN DUAL-GRATING-GATE HEMT'S." International Journal of High Speed Electronics and Systems 19, no. 01 (March 2009): 33–53. http://dx.doi.org/10.1142/s0129156409006072.

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Two dimensional plasmons in submicron transistors have attracted much attention due to their nature of promoting emission/detection of electromagnetic radiation in the terahertz range. We have recently proposed and fabricated a highly efficient, broadband plasmon-resonant terahertz emitter. The device incorporates doubly interdigitated grating gates and a vertical cavity into a high electron mobility transistor. The device operates in various modes: (1) DC-current-driven self oscillation, (2) CW-laser excited terahertz emission, (3) two-photon injection-locked difference-frequency terahertz emission, and (4) impulsive laser excited terahertz emission. Furthermore, the device can operate in completely different functionalities including ultrahigh-speed intensity modulation for terahertz carrier waves. This paper reviews recent advances on plasma wave devices.

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Fu, Yuan, Xiaojian Fu, Lei Shi, and Tie Jun Cui. "Grating-like Terahertz Metasurface for Large-Deflection-Angle Beam Manipulations." Applied Sciences 12, no. 23 (December 2, 2022): 12322. http://dx.doi.org/10.3390/app122312322.

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Multifunctional terahertz beam manipulations have attracted much attention because of the potential for wide-scale applications in terahertz imaging, communications, etc. In this work, a grating-like terahertz reflective-type metasurface is designed for terahertz beam manipulations on the basis of a frequency-scanning mechanism. The theoretical calculation based on the grating principle has predicted that the metasurface grating can steer the deflected beam from 59.5° to 47.3° as the frequency of the perpendicularly incident terahertz wave changes between 0.87 and 1.02 THz. The large-deflection-angle frequency-scanning performance is validated by both numerical simulations and experimental tests. The metasurface grating developed in this work possesses the potential for applications in terahertz beam steering and beam-splitting devices.

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Sabluk, Andrey V., and Alexey A. Basharin. "Metamaterial-based terahertz converter." Modern Electronic Materials 8, no. 4 (December 19, 2022): 149–55. http://dx.doi.org/10.3897/j.moem.8.4.98919.

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Since the early 1980s the terahertz range (0.1 to 10 THz) attracts permanent attention of fundamental and applied science. Due to its unique properties terahertz radiation is used in a wide range of applications such as spectroscopy, non-destructive defectoscopy and security systems. The design of high-efficiency terahertz absorbers and converters is currently the main task in the development of terahertz technologies. In this work a frequency selective high-Q metamaterial is used for the fabrication of a terahertz-to-infrared converter. The converter consists of a metamaterial-based terahertz absorber coated with a micrometer-thick graphite layer that reemits the absorbed energy in the infrared range. We have carried out electrodynamic and the related thermodynamic calculations of the suggested radiation converter. Numerical simulations yield an electromagnetic radiation absorption coefficient of 99.998% and an analytically calculated converter efficiency of 93.8%. Thanks to these advanced parameters suggested terahertz converter can find it’s applications in a wide range of transportation security inspection and defectoscopy tasks.

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Nikolaev, Nikolay Vladimirovich, Vladimir Viktorovich Il'in, Artem Maksimovich Sokolov, and Elena Evgen'evna Matskevich. "Application of terahertz (sub-terahertz) inspection systems in the integrated security systems." Вопросы безопасности, no. 4 (April 2021): 39–49. http://dx.doi.org/10.25136/2409-7543.2021.4.36822.

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The subject of this research is methods of application of terahertz (sub-terahertz) inspection systems for detecting concealed carry weapon, makeshift explosive devices made of nonstandard materials and other prohibited substances. The object of this research is the detection of concealed carry weapon, makeshift explosive devices made of nonstandard materials and other prohibited substances. The authors examine the application of terahertz (sub-terahertz) inspection systems of compact and portal (stationary) types in the integrated security systems. Special attention is given to the options of using these complexes for expanding the capabilities of the subsystems of video monitoring and detection of sabotage and terrorist means. The conclusion is made on the need to develop the tactics for application of the existing systems of personal security screening, the operation of which is based on radio camera imaging in terahertz (sub-terahertz) frequency range. The authors’ special contribution lies in formulation of recommendations that contain the options of using terahertz (sub-terahertz) inspection systems of various types for detecting concealed carry weapon, makeshift explosive devices made of nonstandard materials and other prohibited substances. The acquire results would help to improve the efficiency of organizing the onsite pass control. The scientific novelty consists in fact that the authors are first within the framework of development of the tactic of using terahertz (sub-terahertz) inspection system to develop proposals of implementation of such means as part of the integrated security systems for detecting concealed carry weapon, makeshift explosive devise made of nonstandard materials and other prohibited substances that differ in carrying out the inspection procedures.

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Minin, Igor V., and Oleg V. Minin. "MILLIMETER AND TERAHERTZ RADIATION DETECTOR." Vestnik SSUGT (Siberian State University of Geosystems and Technologies) 26, no. 4 (2021): 160–75. http://dx.doi.org/10.33764/2411-1759-2021-26-4-160-175.

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The aim of this work is an analytical review of terahertz and millimeter-wave radiation receivers. Classification of terahertz radiation receivers and their comparative characteristics are made. Various aspects of the application of terahertz radiation, as well as the main types and types of receivers of this radiation, are considered in this paper. Photon and thermal receivers, terahertz receivers based on Go-lay cells, and terahertz-to-infrared convectors are analyzed. As a result, a method for increasing the sensitivity of electromagnetic radiation receivers based on the application of the photon jet effect is proposed.

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Sazonov, S. V., and N. V. Ustinov. "New Soliton Regime of Generation of Broadband Terahertz Radiation by Laser Pulses with Tilted Wave Fronts." JETP Letters 118, no. 6 (September 2023): 408–13. http://dx.doi.org/10.1134/s0021364023602531.

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A new soliton-like regime of generation of terahertz radiation by optical pulses with tilted wave fronts is analyzed. It has been shown that the diffraction of an optical pulse is of fundamental importance for the formation of optical–terahertz soliton. A nonsoliton broadband terahertz component is generated synchronously with the soliton component of radiation. Two matching conditions called “super-Cherenkov” and “anti-Cherenkov” have been revealed under which generation is the most efficient. In the former and latter cases, the optical terahertz soliton propagates ahead and behind the nonsoliton terahertz component, respectively.

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Jiang, Huimin, Qingjun Li, Yan Shen, Hangyu Zhou, Yuchai Li, Bo Su, and Cunlin Zhang. "Terahertz Spectral Characteristics of Konjac Gum Determined via Microfluidic Technology." International Journal of Optics 2022 (June 6, 2022): 1–7. http://dx.doi.org/10.1155/2022/1358756.

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Terahertz radiation enables nondestructive testing of biological samples, but is challenged by its high absorption in aqueous samples, so microfluidic technology is introduced to reduce the absorption. In this study, we designed a special temperature control device and an electric field device for a microfluidic chip to examine the terahertz spectral characteristics of konjac gum at different temperatures, concentrations, and electric field exposure time using the terahertz time domain spectroscopy system. Results demonstrate that higher concentrations of konjac gum lead to higher transmission intensity of terahertz radiation and a lower absorption of the radiation. Higher temperatures of the konjac gum lead to lower terahertz transmittance, and longer exposure time in the electric field leads to a lower transmittance of terahertz radiation and its higher absorption by the konjac gum. At the same time, we explain this phenomenon from the perspective of micromolecules. This study provides technical guidance for the detection of konjac gum by terahertz technology.

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Sabluk, A. V., and A. A. Basharin. "Terahertz radiation converter based on metamaterial." Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering 26, no. 1 (April 14, 2023): 56–65. http://dx.doi.org/10.17073/1609-3577-2023-1-56-65.

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Since the early 1980s, the terahertz range (from 0.1 to 10 THz) attracts constant attention of both fundamental and applied physics. Due to its unique properties, terahertz radiation finds it’s applications in spectroscopy, defectoscopy, and security systems. The construction of efficient absorbers and converters in terahertz range is crucial for further development of terahertz technologies. In this work, we use a frequency-selective high-Q metamaterial to construct a converter of terahertz radiation into the infrared radiation. The converter consists of a metamaterial absorber of terahertz radiation covered with a micrometer thick layer of graphite, which emits in the infrared range the energy absorbed by the metamaterial. We have made a numerical electrodynamic and associated thermal simulation of the radiation converter. The metamaterial simulation at 96 GHz (low opacity window of the atmosphere) shows the electromagnetic radiation absorption coefficient of 99.998%, and the analytically calculated converter efficiency of 93.8%. Concluding the above our terahertz radiation converter may contribute to security systems and defectoscopy setups.

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Shih, Yi-Hong, Harry Miyosi Silalahi, Ting-I. Tsai, Yi-Chen Chen, Jou-Yu Su, Chia-Rong Lee, and Chia-Yi Huang. "Optically Tunable and Thermally Erasable Terahertz Intensity Modulators Using Dye-Doped Liquid Crystal Cells with Metasurfaces." Crystals 11, no. 12 (December 18, 2021): 1580. http://dx.doi.org/10.3390/cryst11121580.

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A terahertz metasurface that is imbedded into a dye-doped liquid crystal (DDLC) cell is fabricated in this work. After the metasurface-imbedded DDLC cell is irradiated with a linearly polarized pump beam, the irradiated cell is measured with a terahertz spectrometer. The irradiation of the pump beam causes the adsorption of the dye on one of the substrates of the cell, scattering incident terahertz waves and decreasing the transmittances of the terahertz metasurface at all the frequencies of its resonance spectrum. In addition, these transmittances decrease with an increase in the irradiation times of the pump beam. The adsorbed dye molecules are erased from the substrate after the cell is heated by a hot plate. The cell has similar spectra before the irradiation of the pump beam and after the heating of the hot plate. The aforementioned results reveal that the metasurface-imbedded DDLC cell is an optically tunable and thermally erasable terahertz intensity modulator. Therefore, this cell has the potential in developing intensity attenuators for terahertz imaging, frequency isolators for terahertz telecommunication, and spatial light modulators for terahertz information encryption and decryption.

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Ren, Xiaozhen, and Yuying Jiang. "Spatial Domain Terahertz Image Reconstruction Based on Dual Sparsity Constraints." Sensors 21, no. 12 (June 15, 2021): 4116. http://dx.doi.org/10.3390/s21124116.

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Terahertz time domain spectroscopy imaging systems suffer from the problems of long image acquisition time and massive data processing. Reducing the sampling rate will lead to the degradation of the imaging reconstruction quality. To solve this issue, a novel terahertz imaging model, named the dual sparsity constraints terahertz image reconstruction model (DSC-THz), is proposed in this paper. DSC-THz fuses the sparsity constraints of the terahertz image in wavelet and gradient domains into the terahertz image reconstruction model. Differing from the conventional wavelet transform, we introduce a non-linear exponentiation transform into the shift invariant wavelet coefficients, which can amplify the significant coefficients and suppress the small ones. Simultaneously, the sparsity of the terahertz image in gradient domain is used to enhance the sparsity of the image, which has the advantage of edge preserving property. The split Bregman iteration scheme is utilized to tackle the optimization problem. By using the idea of separation of variables, the optimization problem is decomposed into subproblems to solve. Compared with the conventional single sparsity constraint terahertz image reconstruction model, the experiments verified that the proposed approach can achieve higher terahertz image reconstruction quality at low sampling rates.

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Duan, Tong-Chuan, Shao-Jian Yan, Yan Zhao, Ting-Yu Sun, Yang-Mei Li, and Zhi Zhu. "Relationship between hydrogen bond network dynamics of water and its terahertz spectrum." Acta Physica Sinica 70, no. 24 (2021): 248702. http://dx.doi.org/10.7498/aps.70.20211731.

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Water is the source of all life. The understanding of the terahertz absorption spectrum of water is the prerequisite for the application of terahertz technology to biomedicine. The choice of terahertz frequency is essential for achieving the biological effects of terahertz with high efficiency and low energy consumption. The complex hydrogen bond network of water possesses a broad terahertz absorption peak. Therefore, it is necessary to study the relation between the dynamics of the hydrogen bond network of water and its terahertz absorption spectrum. However, the research in this field is still lacking. Using molecular dynamics simulation methods, the terahertz absorption spectra of different water models at room temperature and pressure are studied in this work. Furthermore, taking the temperature as a variable, the dependence of the terahertz absorption spectrum of water on the strength of the hydrogen bond network is explored. It is found that rising temperature makes the terahertz absorption spectrum of the hydrogen bond network red-shift, indicating that the center frequency of the spectrum is strongly correlated with the strength of the hydrogen bond. Further studies show that there is a linear relationship between the hydrogen bond lifetime of water and the center frequency of vibration absorption peak of the hydrogen bond network. The underlying mechanism can be disclosed by imitating the hydrogen bonds in the hydrogen bond network as springs then using the spring oscillator model. These findings are conducive to understanding in depth the complex hydrogen bond network dynamics in water and promoting the study of terahertz biological effects.

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Fujita, Kazuue, Seungyong Jung, Yifan Jiang, Jae Hyun Kim, Atsushi Nakanishi, Akio Ito, Masahiro Hitaka, Tadataka Edamura, and Mikhail A. Belkin. "Recent progress in terahertz difference-frequency quantum cascade laser sources." Nanophotonics 7, no. 11 (September 27, 2018): 1795–817. http://dx.doi.org/10.1515/nanoph-2018-0093.

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AbstractTerahertz quantum cascade laser (QCL) sources based on intra-cavity difference frequency generation are currently the only electrically pumped monolithic semiconductor light sources operating at room temperature in the 1–6-THz spectral range. Relying on the active regions with the giant second-order nonlinear susceptibility and the Cherenkov phase-matching scheme, these devices demonstrated drastic improvements in performance in the past several years and can now produce narrow-linewidth single-mode terahertz emission that is tunable from 1 to 6 THz with power output sufficient for imaging and spectroscopic applications. This paper reviews the progress of this technology. Recent efforts in wave function engineering using a new active region design based on a dual-upper-state concept led to a significant enhancement of the optical nonlinearity of the active region for efficient terahertz generation. The transfer of Cherenkov devices from their native semi-insulating InP substrates to high-resistivity silicon substrates resulted in a dramatic improvement in the outcoupling efficiency of terahertz radiation. Cherenkov terahertz QCL sources based on the dual-upper-state design have also been shown to exhibit ultra-broadband comb-like terahertz emission spectra with more than one octave of terahertz frequency span. The broadband terahertz QCL sources operating in continuous-wave mode produces the narrow inter-mode beat-note linewidth of 287 Hz, which indicates frequency comb operation of mid-infrared pumps and thus supports potential terahertz comb operation. Finally, we report the high-quality terahertz imaging obtained by a THz imaging system using terahertz QCL sources based on intra-cavity difference frequency generation.

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Choporova, Yuliya Yu, Maxim G. Vlasenko, Vasily V. Gerasimov, Boris A. Knyazev, Aleksandr A. Nikitin, and Valeriy S. Cherkassky. "Approaching Terahertz Holography Using the Free Electron Laser." Siberian Journal of Physics 5, no. 4 (December 1, 2010): 98–102. http://dx.doi.org/10.54362/1818-7919-2010-5-4-98-102.

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Many experiments in the terahertz region have been performed using low-power shot-pulse wideband sources. Appearance of more intense monochromatic terahertz sources (quantum cascade lasers, free electron lasers) and terahertz image sensors enables the implementation of classical variants of optical techniques in the terahertz range. In this paper we describe a series of experiments to demonstrate feasibility of classic holography at the terahertz range using the Novosibirsk free electron laser. Two imaging techniques have been applied for digital hologram recording. A modified MachZehnder interferometer has been fabricated for recording the reference-beam holograms. In-line holograms have been recorded and reconstructed

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Mokrousova, Daria, Leonid Seleznev, Dmitrii Pushkarev, Georgy Rizaev, Maximilian Levus, Andrey Koribut, and Yakov Grudtsyn. "Directivity Control of Terahertz Radiation from Single-Color Filament Plasma with Polypropylene Pipe." Photonics 10, no. 4 (April 13, 2023): 443. http://dx.doi.org/10.3390/photonics10040443.

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Two-dimensional angular distribution of terahertz emission from single-color filamentation of laser pulses is experimentally studied. The use of a polypropylene pipe makes it possible to transform the angular pattern of terahertz radiation from the original hollow-cone one to a more preferable unimodal structure within the terahertz frequency range. It has been shown that propagation in a dielectric pipe can significantly (up to several orders of magnitude) increase the terahertz radiation amplitude at a required distance. We have also experimentally demonstrated that bending the pipe allows us to control the direction of the terahertz radiation propagation.

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Shi, Wei, Chengang Dong, Lei Hou, Zhiyang Xing, Qian Sun, and Lihao Zhang. "Investigation of aging characteristics in explosive using terahertz time-domain spectroscopy." International Journal of Modern Physics B 33, no. 24 (September 30, 2019): 1950272. http://dx.doi.org/10.1142/s0217979219502722.

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The terahertz absorption spectrum of the five aging explosive samples (PETN, RDX, HMX, LLM-105 and TATB) was measured and calculated by Terahertz time-domain spectroscopy system (THz-TDS) and air-biased coherent detection system (ZAP-ABCD), respectively. In this paper, compared with the unaging explosive, each aging explosive sample’s terahertz time-domain spectra were obtained and the terahertz absorption spectra were calculated by using Fourier transform and Lambert’s law. The results show that there are several terahertz absorption peaks which were called “fingerprint spectra” for different aging explosive samples in the range of 0.3–6.0 THz spectrum. Meanwhile, the results also show that the locations of the characteristic absorption peaks are not the same. Moreover, the unaging and aging explosive samples have obviously different terahertz absorption spectra.

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Journal articles on the topic 'Terahertz'

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