Articles de revues : « TERAHERTZ (THZ) RADIATION »

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Zainullin, F. A., D. I. Khusyainov, M. V. Kozintseva et A. M. Buryakov. « Polarization analysis of THz radiation using a wire grid polarizer and ZnTe crystal ». Russian Technological Journal 10, n^o 3 (9 juin 2022) : 74–84. http://dx.doi.org/10.32362/2500-316x-2022-10-3-74-84.

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Objectives. Terahertz time domain spectroscopy (THz-TDS) is currently a promising research method in pharmacology and medicine due to the high sensitivity of terahertz radiation to the chemical composition and molecular structure of organic compounds. However, due to the chirality of many biomolecules, their analysis is performed by THz irradiation with circular dichroism. In particular, circular dichroism of THz radiation allows the study of “soft” vibrational movements of biomolecules with different chiralities. Therefore, when studying such biological materials, accurate control of THz radiation parameters is essential. The paper describes a method for characterizing THz radiation polarization on the example of a black phosphorus source material.Methods. The analysis of polarization parameters of THz radiation experimentally obtained by THz-TDS and using terahertz polarizers was performed by mathematical modeling of the interaction between THz radiation and a ZnTe crystal as a detector.Results. Two schemes of terahertz spectroscopy with the ZnTe crystal as the detector were discussed in detail. The polarization parameters were determined using one or two wire-grid THz polarizers. An expression for approximating the dependences of the peak-to-peak amplitude of THz radiation on the rotation angle of the wire-grid THz polarizer for these cases was derived. The impact of the terahertz electric field intensity value on the shape of polarization dependences was considered. The rotation angle of the polarization ellipse of THz radiation emitted by the surface of a bulk-layered black phosphorus crystal illuminated by femtosecond laser pulses was determined.Conclusions. The amplitude of the THz radiation electric field intensity begins to impact the shape of polarization dependences when its value becomes comparable to or exceeds 40 kV/cm.

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Zabolotniy, A. G., I. A. Geiko et L. M. Balagov. « Terahertz radiation in ophthalmology (review) ». Acta Biomedica Scientifica 6, n^o 6-1 (28 décembre 2021) : 168–80. http://dx.doi.org/10.29413/abs.2021-6.6-1.20.

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Terahertz (THz) radiation is one of the new, intensively studied interdisciplinary fi elds of scientifi c knowledge, including medicine, in the fi rst decades of the 21st century. At the beginning of this article (review), in a brief form, the basic statements on THz radiation, the main parameters and properties are presented; the modern THz biophtonics technologies used in biology and medicine are considered – THz refl ectometry, THz spectroscopy methods. Then a number of directions and examples of possible use of THz technologies in biology and medicine, including pharmaceuticals, are given. The main part of the review presents the progress of experimental research and the prospects for the clinical application of medical technologies of THz spectroscopy, THz imaging, in ophthalmology in the study of the morphological and functional state of the ocular surface structures, diagnosis, medical testing, and treatment of ophthalmopathology of the ocular surface. The article concludes with a review of experimental studies on the safety of using THz waves for medical diagnostics and treatment of ophthalmopathology. In the fi nal part, the main problems and prospects of introducing medical THz technologies into the clinical practice of an ophthalmologist are considered.

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Khodzitsky, Mikhail K., Petr S. Demchenko, Dmitry V. Zykov, Anton D. Zaitsev, Elena S. Makarova, Anastasiia S. Tukmakova, Ivan L. Tkhorzhevskiy, Aleksei V. Asach, Anna V. Novotelnova et Natallya S. Kablukova. « Photothermal, Photoelectric, and Photothermoelectric Effects in Bi-Sb Thin Films in the Terahertz Frequency Range at Room Temperature ». Photonics 8, n^o 3 (12 mars 2021) : 76. http://dx.doi.org/10.3390/photonics8030076.

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The terahertz frequency range is promising for solving various practically important problems. However, for the terahertz technology development, there is still a problem with the lack of affordable and effective terahertz devices. One of the main tasks is to search for new materials with high sensitivity to terahertz radiation at room temperature. Bi1−xSbx thin films with various Sb concentrations seem to be suitable for such conditions. In this paper, the terahertz radiation influence onto the properties of thermoelectric Bi1−xSbx 200 nm films was investigated for the first time. The films were obtained by means of thermal evaporation in vacuum. They were affected by terahertz radiation at the frequency of 0.14 terahertz (THz) in the presence of thermal gradient, electric field or without these influences. The temporal dependencies of photoconductivity, temperature difference and voltage drop were measured. The obtained data demonstrate the possibility for practical use of Bi1−xSbx thin films for THz radiation detection. The results of our work promote the usage of these thermoelectric materials, as well as THz radiation detectors based on them, in various areas of modern THz photonics.

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Khusyainov, D. I., A. V. Gorbatova et A. M. Buryakov. « Terahertz generation from surface of the bulk and monolayer tungsten diselenide ». Russian Technological Journal 8, n^o 6 (18 décembre 2020) : 121–29. http://dx.doi.org/10.32362/2500-316x-2020-8-6-121-129.

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The study of ultrafast laser interaction with graphene-like materials based on transition metal dichalcogenides attracts most scientific groups. It is connected with potential use of these materials in flexible optoelectronic devices of visible and THz range. In this paper the parameters of generation of terahertz field from the surface of bulk layered crystal and monolayer film of tungsten diselenide are analyzed. Generation of terahertz radiation from the surface of experimental samples was studied by the terahertz time-domain spectroscopy in reflection geometry. Bulk layered crystals of tungsten diselenide were grown by gas transport reactions. Monolayers of tungsten diselenide crystals were grown by chemical vapor deposition on a silicon substrate. The bandwidth of the generated terahertz radiation from the surface of the bulk layered tungsten diselenide crystal was ~ 3.5 THz. For tungsten diselenide monolayer the spectrum bandwidth of the generated THz radiation was ~ 2.5 THz. The peak amplitude of the generated terahertz field for both samples was at a frequency of ~ 1 THz. Research of the influence of the angle of rotation of a polarization plane of optical femtosecond pump on peak-to-peak amplitude of the generated terahertz field from the surface of investigated samples was carried out. Symmetry analysis of the azimuthal dependence of THz radiation made it possible to separate the mechanisms of THz radiation and evaluate their contribution. The analysis results confirm that the only possible contribution to the generation of terahertz radiation in a tungsten diselenide monolayer crystal is the second order nonlinear optical effect – optical rectification. One of the contributions to the generation of tungsten diselenide is a nonlinear-optical effect of the third order – surface optical rectification.

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Pfeifer, Tilo, et Stephan Bichmann. « THz-Imaging on its Way to Industrial Application ». Key Engineering Materials 437 (mai 2010) : 271–75. http://dx.doi.org/10.4028/www.scientific.net/kem.437.271.

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Terahertz radiation, which fills the gap between 100 GHz and 10 THz ( = 30 µm – 3 mm) in the electro-magnetic spectrum, has seldom been used outside of astronomy and other scientific research. However, in recent years there has been a significant interest in investigating THz radiation for different new applications. Especially the ability of terahertz radiation to penetrate deep into many organic materials without the damage associated with ionizing radiation such as X-rays lead to recent interests chiefly in the fields of security technology and biomedical imaging. The attribute of many different materials to be transparent for terahertz radiation, was also the reason for many difficulties in practical applications outside of research. Using radiation that can pass through so many materials so well makes detection difficult. In addition, sources to generate light at terahertz frequencies have suffered from low output intensity and other problems. Since the 1990s, technical breakthroughs in sources and detectors have brought terahertz technology within striking distance of significant commercial markets [1]. The pressure to develop new terahertz sources arose from two dramatically different groups - ultrafast timedomain spectroscopists who wanted to work with longer wavelengths, and long wavelength radio astronomers who wanted to work with shorter wavelengths. Today there are continuous-wave (CW) sources available as well as pulsed sources [2]. The aim of this paper is to provide an overview of key scientific developments which currently represent the basics of the mentioned THz technology. Beginning with the working principle of opto-electronic THz sources and detectors, the paper explains different setups for transmitting and using THz radiation. Furthermore it shows different applications of different business branches and gives an outlook for industrial application in the fields of metrology and quality control.

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Sabluk, A. V., et A. A. Basharin. « Terahertz radiation converter based on metamaterial ». Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering 26, n^o 1 (14 avril 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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Zhao, Li, Ruhan Yi, Sun Liu, Yunliang Chi, Shengzhi Tan, Ji Dong, Hui Wang et al. « Biological responses to terahertz radiation with different power density in primary hippocampal neurons ». PLOS ONE 18, n^o 1 (20 janvier 2023) : e0267064. http://dx.doi.org/10.1371/journal.pone.0267064.

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Terahertz (THz) radiation is a valuable imaging and sensing tool which is widely used in industry and medicine. However, it biological effects including genotoxicity and cytotoxicity are lacking of research, particularly on the nervous system. In this study, we investigated how terahertz radiation with 10mW (0.12 THz) and 50 mW (0.157 THz) would affect the morphology, cell growth and function of rat hippocampal neurons in vitro.

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Zhang, Xingyun, Fangyuan Zhan, Xianlong Wei, Wenlong He et Cunjun Ruan. « Performance Enhancement of Photoconductive Antenna Using Saw-Toothed Plasmonic Contact Electrodes ». Electronics 10, n^o 21 (4 novembre 2021) : 2693. http://dx.doi.org/10.3390/electronics10212693.

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A photoconductive logarithmic spiral antenna with saw-toothed plasmonic contact electrodes is proposed to provide a higher terahertz radiation compared with the conventional photoconductive antenna (PCA). The use of saw-toothed plasmonic contact electrodes creates a strong electric field between the anode and cathode, which generates a larger photocurrent and thereby effectively increases the terahertz radiation. The proposed PCA was fabricated and measured in response to an 80 fs optical pump from a fiber-based femtosecond laser with a wavelength of 780 nm. When the proposed antenna is loaded with an optical pump power of 20 mW and a bias voltage of 40 V, a broadband pulsed terahertz radiation in the frequency range of 0.1–2 THz was observed. Compared to the conventional PCA, the THz power measured by terahertz time domain spectroscopy (THz-TDS) increased by an average of 10.45 times.

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Fu, Xiao Jian, et Ji Zhou. « The Applications of Terahertz Spectroscopy in Functional Optical Materials Researches ». Applied Mechanics and Materials 320 (mai 2013) : 133–37. http://dx.doi.org/10.4028/www.scientific.net/amm.320.133.

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Terahertz radiation refers to the electromagnetic wave whose frequency is usually defined between 0.1 and 10 THz (1 THz=1012 Hz). With the development of the emission and detection technologies of THz radiation, terahertz time-domain spectroscopy (THz-TDS) has been widely used in medical diagnosis, security inspection and materials characterization. In this paper, we introduced briefly the progress of terahertz measurement technologies, and then reviewed the applications of THz spectra in functional materials researches. As two important functional optical materials, TiO2 nanoparticles and yttrium aluminum garnet (YAG) crystal have been investigated with THz-TDS. We introduced the electron injection process in TiO2 studied by time resolved THz spectroscopy which is reported in the literature, and then presented our own work, the THz optical constants of undoped and Tm3+ doped YAG crystals.

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Sidorov A. V., Veselov A. P., Vodopyanov A. V., Kubarev V. V., Gorbachev Ya. I. et Shevchenko O. A. « Features of the breakdown in heavy noble gases under the action of Novosibirsk free electron laser radiation ». Technical Physics Letters 49, n^o 2 (2023) : 14. http://dx.doi.org/10.21883/tpl.2023.02.55362.19424.

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The results of experimental studies on the breakdown of noble gases (argon and krypton) by terahertz radiation from the Novosibirsk free electron laser (NovoFEL) are presented. For the first time, the breakdown thresholds of noble gases by terahertz radiation were measured in a wide pressure range (0.2-1.5 bar). Previous experiments to measure breakdown thresholds in the THz range in various gases were carried out for hundreds of GHz or at atmospheric pressure. Experimental breakdown thresholds are compared with calculated data using various simplified models. Keywords: THz radiation, gas breakdown, THz laser discharge.

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STILLMAN, W., C. DONAIS, S. RUMYANTSEV, M. SHUR, D. VEKSLER, C. HOBBS, C. SMITH, G. BERSUKER, W. TAYLOR et R. JAMMY. « SILICON FINFETS AS DETECTORS OF TERAHERTZ AND SUB-TERAHERTZ RADIATION ». International Journal of High Speed Electronics and Systems 20, n^o 01 (mars 2011) : 27–42. http://dx.doi.org/10.1142/s0129156411006374.

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We report on terahertz detection (from 0.2 THz to 2.4 THz) by Si FinFETs of different widths (with 2, 20, and 200 fins connected in parallel). FinFETs (with a small number of fins and with feature sizes as short as 20 nm to 40 nm) showed a very high responsivity (far above that previously measured for standard CMOS). We explain this improvement by negligible narrow channel effects.

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Ma, Shaoqing, Zhiwei Li, Shixiang Gong, Chengbiao Lu, Xiaoli Li et Yingwei Li. « High Frequency Electromagnetic Radiation Stimulates Neuronal Growth and Hippocampal Synaptic Transmission ». Brain Sciences 13, n^o 4 (19 avril 2023) : 686. http://dx.doi.org/10.3390/brainsci13040686.

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Terahertz waves lie within the rotation and oscillation energy levels of biomolecules, and can directly couple with biomolecules to excite nonlinear resonance effects, thus causing conformational or configuration changes in biomolecules. Based on this mechanism, we investigated the effect pattern of 0.138 THz radiation on the dynamic growth of neurons and synaptic transmission efficiency, while explaining the phenomenon at a more microscopic level. We found that cumulative 0.138 THz radiation not only did not cause neuronal death, but that it promoted the dynamic growth of neuronal cytosol and protrusions. Additionally, there was a cumulative effect of terahertz radiation on the promotion of neuronal growth. Furthermore, in electrophysiological terms, 0.138 THz waves improved synaptic transmission efficiency in the hippocampal CA1 region, and this was a slow and continuous process. This is consistent with the morphological results. This phenomenon can continue for more than 10 min after terahertz radiation ends, and these phenomena were associated with an increase in dendritic spine density. In summary, our study shows that 0.138 THz waves can modulate dynamic neuronal growth and synaptic transmission. Therefore, 0.138 terahertz waves may become a novel neuromodulation technique for modulating neuron structure and function.

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Shur, Michael. « Terahertz Sensing Technology ». International Journal of High Speed Electronics and Systems 24, n^o 01n02 (mars 2015) : 1550001. http://dx.doi.org/10.1142/s0129156415500019.

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Sensing applications of THz technology include applications for space exploration, detection of concealed objects, explosive identification, and THz cancer detection. This paper will review these and other emerging applications and existing and potential THz sources and detectors, including photonic and electronic THz devices, such as plasmonic field effect transistors capable of detecting and emitting THz radiation. Plasma wave electronics devices demonstrated THz detection using GaAs-based and GaN-based HEMTs, Si MOS, SOI, and FINFETs and FET arrays. This technology has potential to become a dominant THz electronics technology.

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Burmistrov E. R. et Avakyants L. P. « Determination of 2DEG parameters in LED heterostructures with three quantum wells In-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N/GaN by terahertz time-domain spectroscopy (THz-TDs) ». Physics of the Solid State 65, n^o 2 (2023) : 179. http://dx.doi.org/10.21883/pss.2023.02.55399.503.

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Terahertz time-domain spectroscopy (THz-TDs) has been used to record the resonant frequencies of plasmon oscillations excited in samples of heterostructures with three InxGa1-xN/GaN quantum wells (QWs) by laser pulses with a duration of 130 fs in the temperature range from 90 to 170 K. Fast Fourier transform (FFT) of the time dependence of the electric field of THz-pulses made it possible to obtain the frequency spectra of the power and phase shift of THz-radiation, the interpretation of which made it possible to estimate the pulse relaxation time, mobility and effective mass of two-dimensional electron gas (2DEG) in the heterostructures. Using a series of frequency spectra of the power and phase shift of THz-radiation, the temperature dependences of the effective mass and relaxation time of the 2DEG pulse were obtained. Mobility value 2DEG obtained by the THz-TDs is in good agreement with the data of Hall measurements. Keywords: heterostructures, pulse relaxation time, 2DEG, terahertz radiation, terahertz spectroscopy.

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Makarova E. S., Asach A. V., Tkhorzhevskiy I. L., Sedinin A. D., Zykov D. V., Zaitsev A. D., Demchenko P. et al. « Terahertz radiation detector based on thermoelectric material Bi-=SUB=-88-=/SUB=-Sb-=SUB=-12-=/SUB=--=SUP=-*-=/SUP=- ». Semiconductors 56, n^o 4 (2022) : 257. http://dx.doi.org/10.21883/sc.2022.04.53229.7a.

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Terahertz radiation is very promising for visualization, detection and data transfer. Searching for sensitive, fast and compact THz detector that operates at room temperature is a common subject for these applications. Hence, there is still an issue of searching for new materials for THz radiation detection. Solid solutions based on thermoelectric bismuth and antimony appear to have significant potential for these applications. In this paper photoresponse of thermoelectric material Bi88Sb12 has been studied for the first time. Films with thicknesses of 70 and 150 nm were studied under influence of radiation at frequency of 0.14 THz. Keywords: terahertz radiation, photoresponse, bismuth, antimony, thermoelectric materials, thin films.

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Dolganova, Irina N., Stanislav O. Yurchenko, Valeriy E. Karasik et Vladimir P. Budak. « Peculiarity of Terahertz Waves Scattering ». International Journal of High Speed Electronics and Systems 24, n^o 01n02 (mars 2015) : 1520002. http://dx.doi.org/10.1142/s0129156415200025.

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Scattering of terahertz (THz) radiation is considered to be a significant problem for many applications, since it has often multiple character and is followed by interference effects. We present the computational results of THz propagation through scattering layers, obtained by using Monte Carlo simulation scheme of radiation transfer. Dense package of particles is considered for enhancing the influence of structure factor. Interference effects are shown to play an essential role for scattering phase function and scattering angular distribution of THz radiance.

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Li, Chao, Ya Zhang et Kazuhiko Hirakawa. « Terahertz Detectors Using Microelectromechanical System Resonators ». Sensors 23, n^o 13 (26 juin 2023) : 5938. http://dx.doi.org/10.3390/s23135938.

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The doubly clamped microelectromechanical system (MEMS) beam resonators exhibit extremely high sensitivity to tiny changes in the resonance frequency owing to their high quality (Q-) factors, even at room temperature. Such a sensitive frequency-shift scheme is very attractive for fast and highly sensitive terahertz (THz) detection. The MEMS resonator absorbs THz radiation and induces a temperature rise, leading to a shift in its resonance frequency. This frequency shift is proportional to the amount of THz radiation absorbed by the resonator and can be detected and quantified, thereby allowing the THz radiation to be measured. In this review, we present an overview of the THz bolometer based on the doubly clamped MEMS beam resonators in the aspects of working principle, readout, detection speed, sensitivity, and attempts at improving the performance. This allows one to have a comprehensive view of such a novel THz detector.

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Consolino, Luigi, Annamaria Campa, Davide Mazzotti, Miriam Vitiello, Paolo De Natale et Saverio Bartalini. « Bow-Tie Cavity for Terahertz Radiation ». Photonics 6, n^o 1 (25 décembre 2018) : 1. http://dx.doi.org/10.3390/photonics6010001.

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We report on the development, testing, and performance analysis of a bow-tie resonant cavity for terahertz (THz) radiation, injected with a continuous-wave 2.55 THz quantum cascade laser. The bow-tie cavity employs a wire-grid polarizer as input/output coupler and a pair of copper spherical mirrors coated with an unprotected 500 nm thick gold layer. The improvements with respect to previous setups have led to a measured finesse value F = 123, and a quality factor Q = 5.1·105. The resonator performances and the relevant parameters are theoretically predicted and discussed, and a comparison among simulated and experimental spectra is given.

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Trukhin, Valeriy N., Nikolay N. Zinov’ev, Aleksandr V. Andrianov, Leonid L. Samoilov, Aleksandr O. Golubok, Mikhail L. Felshtyn, Ivan D. Sapozhnikov, Viktor A. Bykov et Aleksandr V. Trukhin. « Terahertz Coherent Scanning Probe Microscope ». Siberian Journal of Physics 5, n^o 4 (1 décembre 2010) : 151–53. http://dx.doi.org/10.54362/1818-7919-2010-5-4-151-153.

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We present the terahertz (THz) scanning probe microscope which combines a THz coherent spectrometer and a scanning probe microscope. It detects forward-scattered radiation and employs harmonic signal demodulation to extract the signal of near-field contribution to scattering of THz electromagnetic waves

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HAN, PENG, KUI-JUAN JIN, YUE-LIANG ZHOU, QING-LI ZHOU et K. HIRAKAWA. « TERAHERTZ RADIATION IN SUPERLATTICES IN MODERATE ELECTRIC FIELD ». International Journal of Modern Physics B 20, n^o 08 (30 mars 2006) : 937–45. http://dx.doi.org/10.1142/s0217979206033693.

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We have studied the terahertz (THz) radiation in superlattices (SLs) in moderate electric field region (between 12 kV/cm and 25 kV/cm) from both theoretical and experimental aspects in this work. The THz emission intensity has been calculated for three samples of GaAs/Al 0.3 Ga 0.7 As SLs by using Kane model. The theoretical results show that the radiation intensity increases until the electric field F achieves a certain value between 14 kV/cm and 16 kV/cm for various samples, and then starts to roll off. The agreement of the calculated results with the experimental data demonstrates that the rolling of THz radiation intensity is due to the competition of field induced localization of wave functions and the increasing of the photon energy in THz radiation with increased electric fields. Furthermore, it is also shown that THz radiation intensity can be affected by the scattering of the randomly distributed Al atoms in the barriers.

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Andrianov A.V, Aleshin A.N., Abolmasov S.N., Terukov E.I. et Zakhar'in A.O. « Excitation of terahertz radiation in p-n-heterostructures based on a-Si:H/c-Si ». Physics of the Solid State 65, n^o 5 (2023) : 814. http://dx.doi.org/10.21883/pss.2023.05.56054.27.

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Studies on the generation of terahertz (THz) radiation in p-n-heterostructures based on a-Si:H/c-Si upon their photoexcitation by a femtosecond titanium-sapphire laser with a wavelength of 800 nm are presented. The properties of observed THz radiation allow to explain its nature by excitation of fast photocurrent of nonequilibrium charge carriers created in the region of the potential barrier under femtosecond interband photoexcitation of the structure. The fast photocurrent, in turn, emits THz electromagnetic waves. The waveforms and amplitude spectra of the observed THz radiation reflect the dynamics of photoexcited charge carriers in the structures. The intensity of THz radiation observed in the studied p-n-heterostructures based on a-Si:H/c-Si is comparable to that generated in n-InAs crystals, which are widely used as emitters in systems of THz time-domain spectroscopy. Therefore, a-Si:H/c-Si p-n-heterostructures can be used as THz emitters for need of THz spectroscopy. Keywords: femtosecond laser photoexcitation, heterostructures, fast photocurrent, terahertz electromagnetic radiation.

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Sinko, Anton, Ilya Ozheredov, Elena Rudneva, Vera Manomenova, Natalia Kozlova, Natalia Lobova, Alexey Voloshin, Jean-Louis Coutaz et Alexander Shkurinov. « Perspective on Terahertz Applications of Molecular Crystals ». Electronics 11, n^o 17 (30 août 2022) : 2731. http://dx.doi.org/10.3390/electronics11172731.

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In this review, we present a survey on the use of molecular nonlinear crystals in the context of terahertz (THz) photonics. The fundamentals of nonlinear optics for converting optical and infrared radiation into THz radiation with the basic theory of femtosecond optical rectification and difference frequency generation are described. Various types of phase-matching conditions that can be achieved in molecular crystals are discussed. It is shown that one of the unique features of molecular crystals is the ability to generate tunable narrowband terahertz radiation using femtosecond lasers. We also provide a detailed description of the most commonly used and promising molecular crystals such as DAST, DSTMS, OH1, HMQ-TMS, DCMBI, and GUHP. This review also presents a description of recent publications which show the prospects of using molecular nonlinear optical crystals in THz photonics.

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Sabluk, Andrey V., et Alexey A. Basharin. « Metamaterial-based terahertz converter ». Modern Electronic Materials 8, n^o 4 (19 décembre 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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Ciccarelli, Chiara, Hannah Joyce, Jason Robinson, Farhan Nur Kholid, Dominik Hamara, Srabani Kar et Kun-Rok Jeon. « Terahertz Time-Domain Spectroscopy ». Scientific Video Protocols 1, n^o 1 (1 février 2020) : 1–4. http://dx.doi.org/10.32386/scivpro.000006.

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Time-Domain terahertz spectroscopy (THz TDS) has attracted attention from many scientific disciplines as it enables accessing the gap between electronic and optical techniques. One application is to probe spintronic dynamics in sub-picosecond time scale. Here, we discuss principles and technical aspects of a typical THz TDS setup. We also show an example of terahertz time-domain data obtained from a Co/Pt thin film calibrant, which is a well-studied spintronic structure emitting strong THz radiation. See video at https://youtu.be/X7vrvQcmy8c.

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Minin, Igor V., et Oleg V. Minin. « PROBLEMS OF TERAHERTZ RADIATION METROLOGY IN MEDICINE ». Vestnik SSUGT (Siberian State University of Geosystems and Technologies) 26, n^o 3 (2021) : 162–80. http://dx.doi.org/10.33764/2411-1759-2021-26-3-162-180.

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The purpose of this work is to consider the issue of safe propagation of terahertz radiation in bio-logical objects. The article gives a brief review of studies of the influence mechanisms of terahertz radiation on biological environments. It considers optical characteristics of blood and its components in the THz frequency range. It is found that the boundaries of the terahertz wavelength range are not precisely defined. It is established that the recently discovered "photon jet" effect allows terahertz ra-diation to penetrate biological objects to considerable depths, due to the effect of a quasi-optical mesoscale waveguide composed of spherical or disk particles. Amplification of small-sized particles that form a photon jet can significantly increase the value of the radiation intensity density at the bio-logical object of study.

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Hu, Qing. « Generation of Terahertz Emission Based on Intersubband Transitions ». International Journal of High Speed Electronics and Systems 12, n^o 04 (décembre 2002) : 995–1024. http://dx.doi.org/10.1142/s0129156402001897.

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In this chapter, we present our work on the development of coherent THz sources based on intersubband transition in quantum-well structures. The main focus is on electrically pumped or quantum-cascade structures, which have been quite successful in generating coherent radiation at mid-infrared frequencies. Relevant issues, such as various depopulation intersubband scattering rates, the role of complex phonon spectra, and coherent vs. incoherent tunneling are discussed in details. Optically pumped sources, including optical parametric amplifiers, and both intersubband and interband pumped THz emitters, are also investigated for their feasibility in generating coherent THz radiations.

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Shi, Jinhui, Zhongjun Li, David K. Sang, Yuanjiang Xiang, Jianqing Li, Shuang Zhang et Han Zhang. « THz photonics in two dimensional materials and metamaterials : properties, devices and prospects ». Journal of Materials Chemistry C 6, n^o 6 (2018) : 1291–306. http://dx.doi.org/10.1039/c7tc05460b.

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Terahertz radiation refers to a broad electromagnetic spectrum range between microwave and infrared waves, which is also known as the terahertz gap due to inadequate materials and technologies for its generation and manipulation.

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Ushakov, Aleksandr, Pavel Chizhov, Vladimir Bukin, Daniil Shipilo, Nikolay Panov, Olga Kosareva et Sergey Garnov. « Multiple Filamentation Effects on THz Radiation Pattern from Laser Plasma in Air ». Photonics 8, n^o 1 (25 décembre 2020) : 4. http://dx.doi.org/10.3390/photonics8010004.

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An experimental study of few filaments interaction impact on the terahertz radiation pattern has demonstrated that interaction of two close propagating beams leads to formation of a superfilament-like structure with on-axis terahertz yield. Mutual delay between two beamlets tilts the output intensity front of THz emission.

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Khabibullin, R. A., S. S. Pushkarev, R. R. Galiev, N. V. Shchavruk, I. N. Dyuzhikov, V. V. Pavlovskiy et O. Yu Volkov. « Spectral Characteristics of Terahertz Quantum Cascade Lasers ». Nano- i Mikrosistemnaya Tehnika 24, n^o 2 (21 février 2022) : 96–102. http://dx.doi.org/10.17587/nmst.24.96-102.

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Terahertz quantum cascade lasers (THz QCLs) are prospective radiation sources for high-resolution gas spectroscopy. A wide range of operating frequencies (from 1.2 to 5.4 THz), a narrow generation line (up to 10 kHz), the ability to operate on several radiative transitions (two-color lasers, generation of frequency combs) and other unique characteristics of THz QCLs make it possible to create a new generation of gas spectrometers for biomedical and environmental applications. The article discusses the possibilities of controlling the spectral characteristics of THz QCLs by changing the operating temperature and parameters of the injection current pulses: amplitude, duration, and repetition rate. For the first time, the study of energy transfer between longitudinal Fabry — Perot modes in THz QCLs with a change in the duty cycle of injection current pulses has been carried out.

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Fujita, Kazuue, Shohei Hayashi, Akio Ito, Masahiro Hitaka et Tatsuo Dougakiuchi. « Sub-terahertz and terahertz generation in long-wavelength quantum cascade lasers ». Nanophotonics 8, n^o 12 (2 novembre 2019) : 2235–41. http://dx.doi.org/10.1515/nanoph-2019-0238.

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AbstractTerahertz quantum cascade laser sources with intra-cavity non-linear frequency mixing are the first room-temperature electrically pumped monolithic semiconductor sources that operate in the 1.2–5.9 THz spectral range. However, high performance in low-frequency range is difficult because converted terahertz waves suffer from significantly high absorption in waveguides. Here, we report a sub-terahertz electrically pumped monolithic semiconductor laser. This sub-terahertz source is based on a high-performance, long-wavelength (λ ≈ 13.7 μm) quantum cascade laser in which high-efficiency terahertz generation occurs. The device produces peak output power of 11 μW within the 615–788 GHz frequency range at room temperature. Additionally, a source emitting at 1.5 THz provides peak output power of 287 μW at 110 K. The generated terahertz radiation of <2 THz is mostly attributable to the optical rectification process in long-wavelength infrared quantum cascade lasers.

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Wang, Kemeng, Yangfan Gu, Yongchang Lu, Jianqiang Gu et Weili Zhang. « Terahertz radiation enhancement in gallium arsenide nano-hole array under low power optical pump ». Applied Physics Letters 121, n^o 7 (15 août 2022) : 071703. http://dx.doi.org/10.1063/5.0099288.

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Though accelerating photocarriers by the semiconductor surface electric field is the simplest way to generate broadband terahertz pulses, the weak THz power under low optical pump hinders its application in these compact systems. Here, we report a ⟨100⟩ semi-insulating gallium arsenide nano-hole array under above-the-bandgap excitation, which boosts terahertz emission power up to 5.75 folds of bare gallium arsenide with a 32 mW pump. The nano-structured array lifts the absorption of the optical pump and localizes the photocarriers near the surface of gallium arsenide, benefiting the transient photocurrents and thus the THz power. Interestingly, the enhancement is poorly related to the terahertz frequency, and the power difference of the emitted THz wave under the TE and TM pumps is greatly smoothed. In addition, the THz emission enhancement of the nanoscale hole arrays favors a low-power pump. The demonstration shown here provides a potential route for advancing the weak THz power of surface emission, which will promote the application of the surface emitting THz source in the practical THz systems employing compact femtosecond lasers.

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Wang, Kemeng, Jianqiang Gu, Wenqiao Shi, Youwen An et Weili Zhang. « Terahertz photoconductive antenna with all-dielectric nanopillars ». Terahertz Science and Technology 13, n^o 3 (septembre 2020) : 112–18. http://dx.doi.org/10.1051/tst/2020133112.

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Photoconductive antennas (PCAs), as a popular terahertz (THz) radiation source, have been widely used in spectroscopy, material characterization, biological imaging and detection of hazardous materials. However, PCAs have a relatively low energy conversion efficiency from femtosecond laser pulses to THz radiation which often limits the signal-to-noise ratio and bandwidth of THz imaging and spectroscopy systems. To address these limitations, here we report a THz photoconductive antenna emitter with all-dielectric nanopillars integrated on top of the SI-GaAs substrate to increase the generated photocarriers, which achieves a broadband and frequency insensitive THz power enhancement factor around 1.25 at frequencies 0.05 - 1.6 THz. Our results reported here provide a new method for increasing the THz power of PCAs, which paves the way for the subsequent researches of next-generation PCAs.

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Gorlova, D., I. Tsymbalov, R. Volkov et A. Savel’ev. « Transition radiation in the THz range generated in the relativistic laser—tape target interaction ». Laser Physics Letters 19, n^o 7 (26 mai 2022) : 075401. http://dx.doi.org/10.1088/1612-202x/ac6fcb.

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Abstract Generation of terahertz (THz) radiation in the interaction of laser pulse with intensity ∼5 × 1018 W cm−2 with a controlled preplasma, created by an additional laser pulse interacting with a 16 μm film target, was studied. The mechanism of generation of THz radiation in the frequency range 1–5 THz was found to be coherent transition radiation of accelerated electrons transversing the rear plasma-vacuum boundary. Angular distribution of the THz radiation changes with the delay between main pulse and prepulse due to different regimes of electron acceleration, while THz radiation spectrum reflects the spatial size of the preplasma cloud and may be used for diagnostics purposes. THz radiation energy reaches ∼0.1 mJ in 1–5 THz spectral range, corresponding to 0.2% conversion efficiency, and increases linearly with laser pulse energy.

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Bakhtiari, Farhad, Masoud Yousefi, Shole Golmohammady, Seyed Masoud Jazayeri et Bijan Ghafary. « Generation of terahertz radiation by beating of two circular flat-topped laser beams in collisional plasma ». Laser and Particle Beams 33, n^o 4 (15 octobre 2015) : 713–22. http://dx.doi.org/10.1017/s026303461500083x.

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AbstractThis paper presents a scheme of terahertz (THz) radiation generation based on beating of two flat-topped laser beams by different frequencies and the same electric field amplitudes in actual plasma with spatially periodic density that electron–neutral collisions have been taken into account. Flat-topped laser beams have the exclusive features such as steep gradient in distribution of laser intensities, wider cross-section in comparison with other profiles, which make stronger ponderomotive force and lead to stronger nonlinear current and hence, THz radiation of higher field. The effects of laser and plasma parameters on THz radiation generation are investigated analytically. It is shown that by increasing the order of flatness of incident laser beams, because of their steep gradient, good enhancement in emitted THz radiation take place. It can be deduced that by increasing beating frequency, efficiency of THz generation decreases which can be compensated by manipulating in density ripple magnitudes. The intensity of the emitted radiations is found to be highly sensitive to the order of flatness. Based on the results of this paper, optimization of laser and plasma parameters can increase the efficiency of THz radiation generation strongly.

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Черкасова, О. П., Д. С. Сердюков, А. С. Ратушняк, Е. Ф. Немова, Е. Н. Козлов, Ю. В. Шидловский, К. И. Зайцев et В. В. Тучин. « Механизмы влияния терагерцового излучения на клетки (обзор) ». Журнал технической физики 128, n^o 6 (2020) : 852. http://dx.doi.org/10.21883/os.2020.06.49420.51-20.

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Terahertz (THz) radiation and related technologies are rapidly developed and find their application in different branches of science and technology, including medical diagnostics and therapy. This poses a problem of determining the safety limits of the human body exposure to THz radiation, which is closely related to a problem of biological activity of THz waves. Therefore, in this work, the current state of research in the area of THz radiation – cells interaction is overviewed.

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Ardaneh, Kazem, Ken-Ichi Nishikawa, Remo Giust, Benoit Morel, Pierre-Jean Charpin, Arnaud Couairon, Guy Bonnaud et Francois Courvoisier. « Femtosecond laser-induced sub-wavelength plasma inside dielectrics. III. Terahertz radiation emission ». Physics of Plasmas 30, n^o 1 (janvier 2023) : 013301. http://dx.doi.org/10.1063/5.0126427.

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Electromagnetic radiation within the terahertz (THz) frequency range is of great interest for applications in remote sensing and time-domain spectroscopy. The laser-induced plasmas are promising mediums for generating THz radiation. It has been recently reported that focusing femtosecond Bessel pulses inside dielectrics induces a high aspect ratio over-critical plasmas. Here, we show that the intense resonantly driven electrostatic fields at the so-called critical surface lead to THz radiation emission. Through three-dimensional particle-in-cell simulation and analytical derivation, we have investigated the emission of THz radiation. We show that the THz radiation is associated with a hot population of electrons trapped in ambipolar electric fields of the double layers.

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Алексеев, П. А., Б. Р. Бородин, И. А. Мустафин, А. В. Зубов, С. П. Лебедев, А. А. Лебедев et В. Н. Трухин. « Терагерцевый ближнепольный отклик в лентах графена ». Письма в журнал технической физики 46, n^o 15 (2020) : 29. http://dx.doi.org/10.21883/pjtf.2020.15.49745.18256.

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The experimental results of scattering and near-field interaction of a terahertz electromagnetic field with graphene ribbons near a metal probe of an atomic force microscope are reported. The amplification of a near-field terahertz scattering in ribbons is shown in comparison with unstructured graphene. The appearance of resonance peaks in the range 0.2–1.6 THz in the scattering spectra of terahertz radiation on graphene ribbons in the presence of a probe was detected, which is possibly due to the interaction of radiation with plasmons in the ribbons.

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Chen, Shuqing, Zhiqiang Xie, Junmin Liu, Yanliang He, Yao Cai, Xiaoke Zhang, Jiangnan Xiao, Ying Li et Dianyuan Fan. « Effective Generation of Milliwatt-Level Sub-Terahertz Wave for Nonlinear Response Measurement of Two-Dimensional Material by Optical Heterodyne Technique ». Advances in Condensed Matter Physics 2017 (2017) : 1–9. http://dx.doi.org/10.1155/2017/1704374.

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By using optical heterodyne technique, we demonstrated the stable emission of sub-terahertz wave with the frequency ranging from 88 GHz to 101 GHz, which can operate as microwave source for nonlinear response measurement system. Mutual frequency beating of two well-separated sideband signals at a 0.1 THz photo-detector (PD) allows for the generation of sub-terahertz signal. Based on this approach, we have achieved the radiation of 0.1 THz wave with power up to 4 mW. By transmittance measurement, two-dimensional nanomaterial topological insulator (TI: Bi2Te3) shows saturable absorption behaviors with normalized modulation depth of 47% at 0.1 THz. Our results show that optical heterodyne technique could be developed as an effective microwave source generation for nonlinear measurement at sub-terahertz, even terahertz band.

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Thakur, Vishal, Niti Kant et Sandeep Kumar. « THz Field Enhancement under the Influence of Cross-focused Laser Beams in the m-CNTs ». Trends in Sciences 20, n^o 6 (15 mars 2023) : 5284. http://dx.doi.org/10.48048/tis.2023.5284.

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In the present analysis, we have studied the effect of cross-focused Gaussian laser beams propagating through the array of magnetized carbon nanotubes (m-CNTs) to enhance the terahertz (THz) field amplitude of emitted radiation. The plasma present in the form of CNTs rearranges itself due to the ponderomotive nonlinearity, which gives rise to the nonlinear optical phenomenon known as the cross-focusing of laser beams. The ponderomotive nonlinearity, cross-focusing of lasers, and anharmonic behavior of m-CNTs are responsible for the very strong nonlinear current density in the system. The cross-focusing effect of the propagating Gaussian laser beams increases with the increase in the externally applied static magnetic field, which is applied along the longitudinal axis of the CNTs. As a result, the normalized THz field amplitude shows a significant enhancement, and the THz radiations emitted in this way can be utilized in biological diagnosis (of the living beings) instead of X-rays. The internal and external diameters of the CNTs also make a notable impact on the THz field amplitude. HIGHLIGHTS We have studied the effect of cross-focused laser beams propagating through the magnetized carbon nanotubes to enhance the terahertz field of emitted radiation The ponderomotive nonlinearity, cross-focusing of lasers, and anharmonic behavior are responsible for the strong nonlinear current density in the system The internal and external diameters of the m- CNTs also make a notable impact on the THz field amplitude The frequency of emitted radiation shows that these can be utilized in the biological diagnosis of living beings instead of X-rays GRAPHICAL ABSTRACT

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Klier, Jens, Garik Torosyan, Nina Susan Schreiner, Daniel Molter, Frank Ellrich, Wissem Zouaghi, Emilien Peytavit et al. « Influence of Substrate Material on Radiation Characteristics of THz Photoconductive Emitters ». International Journal of Antennas and Propagation 2015 (2015) : 1–7. http://dx.doi.org/10.1155/2015/540175.

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We present in this paper spectral and spatial characteristics of terahertz emission from standard dipole antenna structures used as emitters depending on the substrate material. All antenna structures were lithographically fabricated on low-temperature (LT) grown, few-micrometers-thick gallium arsenide (GaAs) layers. To investigate the effect of the substrate material on the radiation pattern of terahertz beams, either semi-insulating gallium arsenide or high-resistivity silicon substrate wafers have been used. As detector a standard 40 µm long dipole antenna on a semi-insulating GaAs substrate with a low-temperature grown gallium arsenide layer on it has been employed; this configuration allows for broadband detection and is still efficient enough for the characterization purpose. Strong dependence of the radiation pattern on the substrate used for the terahertz source is demonstrated. The measured patterns and differences between the two cases of substrates are well explained by means of classical diffraction.

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Kuznetsov, Kirill A., Sergey A. Tarasenko, Polina M. Kovaleva, Petr I. Kuznetsov, Denis V. Lavrukhin, Yury G. Goncharov, Alexander A. Ezhov, Dmitry S. Ponomarev et Galiya Kh Kitaeva. « Topological Insulator Films for Terahertz Photonics ». Nanomaterials 12, n^o 21 (26 octobre 2022) : 3779. http://dx.doi.org/10.3390/nano12213779.

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We discuss experimental and theoretical studies of the generation of the third terahertz (THz) frequency harmonic in thin films of Bi2Se3 and Bi2-xSbxTe3-ySey (BSTS) topological insulators (TIs) and the generation of THz radiation in photoconductive antennas based on the TI films. The experimental results, supported by the developed kinetic theory of third harmonic generation, show that the frequency conversion in TIs is highly efficient because of the linear energy spectrum of the surface carriers and fast energy dissipation. In particular, the dependence of the third harmonic field on the pump field remains cubic up to the pump fields of 100 kV/cm. The generation of THz radiation in TI-based antennas is obtained and described for the pump, with the energy of photons corresponding to the electron transitions to higher conduction bands. Our findings open up possibilities for advancing TI-based films into THz photonics as efficient THz wave generators and frequency converters.

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Kong, Huiyan, Luyi Huang, Min Li, Ling Zhang et Heping Zeng. « Enhancement of Terahertz Radiation by Surface Plasmons Based on CdTe Thin Films ». Nanomaterials 12, n^o 2 (17 janvier 2022) : 290. http://dx.doi.org/10.3390/nano12020290.

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Terahertz (THz) time-domain spectroscopy (TDS) is a powerful tool used to characterize the surface/interface of materials, and semiconductor/metal interfaces can generate THz emission through ultrafast optical excitation, which can be further improved through the optical excitation of surface plasmons. Here, we assembled cadmium telluride (CdTe) on an AuAg alloy (Au25Ag75, wt.%) substrate and obtained five times stronger THz emission compared with silicon substrate, and found that the enhancement can be tuned by controlling the thickness of the semiconductor materials and plasmonic metal substrates. We believe that our results not only promote the development of THz emission enhancement, but also provide a straightforward way of producing small, thin, and more efficient terahertz photonic devices.

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Veselov A. P., Sidorov A. V., Kalynov Yu. K. et Vodopyanov A. V. « Discharge of heavy noble gases induced by pulsed gyrotron radiation with 1 THz frequency ». Technical Physics Letters 49, n^o 3 (2023) : 70. http://dx.doi.org/10.21883/tpl.2023.03.55691.19445.

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In this work, gas discharge ignited by girotron radiation with frequency 1 THz was carried out. Breakdown curves were calculated both for selfignited and initiated discharges. There was shown that in a case of breakdown by the pulse radiation with duration longer than several microseconds electric field threshold is the same as in a case of continuous wave breakdown. Also, the possibility of using a terahertz gyrotron as a radiation source for discharge in gas targets on installations for extreme ultraviolet photolithography was assessed. Keywords: girotron, terahertz breakdown, extreme ultraviolet lithography.

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Shur, Michael, Gregory Aizin, Taiichi Otsuji et Victor Ryzhii. « Plasmonic Field-Effect Transistors (TeraFETs) for 6G Communications ». Sensors 21, n^o 23 (27 novembre 2021) : 7907. http://dx.doi.org/10.3390/s21237907.

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Ever increasing demands of data traffic makes the transition to 6G communications in the 300 GHz band inevitable. Short-channel field-effect transistors (FETs) have demonstrated excellent potential for detection and generation of terahertz (THz) and sub-THz radiation. Such transistors (often referred to as TeraFETs) include short-channel silicon complementary metal oxide (CMOS). The ballistic and quasi-ballistic electron transport in the TeraFET channels determine the TeraFET response at the sub-THz and THz frequencies. TeraFET arrays could form plasmonic crystals with nanoscale unit cells smaller or comparable to the electron mean free path but with the overall dimensions comparable with the radiation wavelength. Such plasmonic crystals have a potential of supporting the transition to 6G communications. The oscillations of the electron density (plasma waves) in the FET channels determine the phase relations between the unit cells of a FET plasmonic crystal. Excited by the impinging radiation and rectified by the device nonlinearities, the plasma waves could detect both the radiation intensity and the phase enabling the line-of-sight terahertz (THz) detection, spectrometry, amplification, and generation for 6G communication.

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Wang, Lulu. « Terahertz Imaging for Breast Cancer Detection ». Sensors 21, n^o 19 (28 septembre 2021) : 6465. http://dx.doi.org/10.3390/s21196465.

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Terahertz (THz) imaging has the potential to detect breast tumors during breast-conserving surgery accurately. Over the past decade, many research groups have extensively studied THz imaging and spectroscopy techniques for identifying breast tumors. This manuscript presents the recent development of THz imaging techniques for breast cancer detection. The dielectric properties of breast tissues in the THz range, THz imaging and spectroscopy systems, THz radiation sources, and THz breast imaging studies are discussed. In addition, numerous chemometrics methods applied to improve THz image resolution and data collection processing are summarized. Finally, challenges and future research directions of THz breast imaging are presented.

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Grigelionis, Ignas, et Irmantas Kašalynas. « Terahertz Spectroscopy of Thermal Radiation from AlGaN/GaN Heterostructure on Sapphire at Low Temperatures ». Applied Sciences 10, n^o 3 (25 janvier 2020) : 851. http://dx.doi.org/10.3390/app10030851.

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Terahertz spectroscopy of thermal radiation from electrically pumped AlGaN/GaN structures on sapphire substrate was investigated in this work. Comparison of experimental THz spectroscopy results to theoretical spectra calculations shows that thermal radiation of the sample lattice is the main mechanism causing the emission above T = 155 K, and it is mainly influenced by sapphire substrate. Here, the emission was attributed to the radiative electron transitions in shallow impurities and nitrogen vacancies as well as to radiative decay of longitudinal optical phonons (387 cm - 1 ) in sapphire substrate. We have successfully demonstrated that THz emission spectroscopy can be used to define the temperature at which thermal emission from AlGaN/GaN HEMT structures dominates the emission spectrum.

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Bannikova, Svetlana, Tamara Khlebodarova, Asya Vasilieva, Irina Mescheryakova, Alla Bryanskaya, Elizaveta Shedko, Vasily Popik, Tatiana Goryachkovskaya et Sergey Peltek. « Specific Features of the Proteomic Response of Thermophilic Bacterium Geobacillus icigianus to Terahertz Irradiation ». International Journal of Molecular Sciences 23, n^o 23 (2 décembre 2022) : 15216. http://dx.doi.org/10.3390/ijms232315216.

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Studying the effects of terahertz (THz) radiation on the proteome of temperature-sensitive organisms is limited by a number of significant technical difficulties, one of which is maintaining an optimal temperature range to avoid thermal shock as much as possible. In the case of extremophilic species with an increased temperature tolerance, it is easier to isolate the effects of THz radiation directly. We studied the proteomic response to terahertz radiation of the thermophilic Geobacillus icigianus, persisting under wide temperature fluctuations with a 60 °C optimum. The experiments were performed with a terahertz free-electron laser (FEL) from the Siberian Center for Synchrotron and Terahertz Radiation, designed and employed by the Institute of Nuclear Physics of the SB of the RAS. A G. icigianus culture in LB medium was THz-irradiated for 15 min with 0.23 W/cm2 and 130 μm, using a specially designed cuvette. The life cycle of this bacterium proceeds under conditions of wide temperature and osmotic fluctuations, which makes its enzyme systems stress-resistant. The expression of several proteins was shown to change immediately after fifteen minutes of irradiation and after ten minutes of incubation at the end of exposure. The metabolic systems of electron transport, regulation of transcription and translation, cell growth and chemotaxis, synthesis of peptidoglycan, riboflavin, NADH, FAD and pyridoxal phosphate cofactors, Krebs cycle, ATP synthesis, chaperone and protease activity, and DNA repair, including methylated DNA, take part in the fast response to THz radiation. When the response developed after incubation, the systems of the cell’s anti-stress defense, chemotaxis, and, partially, cell growth were restored, but the respiration and energy metabolism, biosynthesis of riboflavin, cofactors, peptidoglycan, and translation system components remained affected and the amino acid metabolism system was involved.

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Ezhov, Dmitry, Nazar Nikolaev, Valery Antsygin, Sofia Bychkova, Yury Andreev et Valery Svetlichnyi. « Temperature-Dependent Optical Properties of Bismuth Triborate Crystal in the Terahertz Range : Simulation of Terahertz Generation by Collinear Three-Wave Mixing in the Main Crystal Planes ». Photonics 10, n^o 7 (22 juin 2023) : 713. http://dx.doi.org/10.3390/photonics10070713.

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Terahertz (THz) frequency generation via nonlinear optical techniques is of particular interest due to the immense potential of this type of radiation in various scientific fields, ranging from medicine to telecommunications. Selecting suitable nonlinear media for laser frequency down-conversion presents a challenging task. Considering an approach that uses nonlinear crystals with high radiation resistance, pumped by intense laser pulses near their damage threshold, we suggest the crystal of bismuth triborate (BiB3O6, BIBO). Compared to other borate-class crystals, BIBO exhibits relatively high coefficients of quadratic susceptibility. In this paper, we have studied the optical properties of BIBO samples in a wide spectral range from 0.1 to 2.1 THz at temperatures of 473, 383, 295, and 77 K using Terahertz Time-Domain Spectroscopy (THz-TDS). Furthermore, we simulated collinear three-wave interactions with nonzero efficiency for difference frequency generation (DFG) in the THz range. For the pump wavelengths of about 800 nm, we determined phase-matching (PM) conditions and compared the generation efficiency for different crystal cuts. The potential of utilizing BIBO crystal for terahertz frequency generation is discussed.

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Kaijun, Mu, et Zhang Cunlin. « Application of Terahertz Spectroscopy and Imaging ». Siberian Journal of Physics 5, n^o 4 (1 décembre 2010) : 123–29. http://dx.doi.org/10.54362/1818-7919-2010-5-4-123-129.

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We examined the feasibility of Terahertz time-domain spectroscopy (THz-TDS) using a 4-mm-thick quartz crystal to extract the angle of rotation of THz radiation polarization induced by a two-color laser in air plasma. We also used the THz-TDS technique to identify explosives and melamine in mixtures. In addition, we presented a new opto-mechanical scanner for security applications using the method of passive THz imaging

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Rahani, Ehsan Kabiri, Tribikram Kundu, Ziran Wu et Hao Xin. « Heat Induced Damage Detection by Terahertz (THz) Radiation ». Journal of Infrared, Millimeter, and Terahertz Waves 32, n^o 6 (5 avril 2011) : 848–56. http://dx.doi.org/10.1007/s10762-011-9784-7.

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