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Baksheeva K, Vdovydchenko A, Gorshkov K, Ozhegov R, Kinev N, Koshelets V, et al. Study of human skin radiation in the terahertz frequency range. In: J. Phys.: Conf. Ser. Vol 1410.; 2019. 012076 (1 to 5).
Abstract: The radiation of human skin in the terahertz frequency range under the influence of mental stresses has been studied in the current work. An experimental setup for observation of changes in human skin radiation, which occur under the influence of psychological stresses, by means of a superconducting integrated receiver has been developed. More than 30 volunteers participate in these studies, which allows us to verify presence of correlation between the signals from the superconducting integrated terahertz receiver and other sensors that monitor human mental stress.
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Polyakova MI, Florya IN, Semenov AV, Korneev AA, Goltsman GN. Extracting hot-spot correlation length from SNSPD tomography data. In: J. Phys.: Conf. Ser. Vol 1410.; 2019. 012166 (1 to 4).
Abstract: We present data of quantum detector tomography for the samples specifically optimized for this problem. Using this method, we take results of hot-spot correlation length of 17 ± 2 nm.
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Rasulova GK, Pentin IV, Goltsman GN. Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations. AIP Advances. 2019;9(10):105220.
Abstract: Radio-frequency modulated terahertz (THz) emission power from weakly-coupled GaAs/AlGaAs superlattice (SL) has been increased by parallel connection of several SL mesas. Each SL mesa is a self-oscillator with its own oscillation frequency and mode. In coupled non-identical SL mesas biased at different voltages within the hysteresis loop the chaotic, quasiperiodic and frequency-locked modes of self-oscillations of current arise. THz emission was detected when three connected in parallel SL mesas were biased into the frequency-locked and quasiperiodic modes of self-oscillations of current, while in the chaotic mode of those it falls to the noise level.
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Elezov M, Ozhegov R, Goltsman G, Makarov V. Countermeasure against bright-light attack on superconducting nanowire single-photon detector in quantum key distribution. Opt Express. 2019;27(21):30979–88.
Abstract: We present an active anti-latching system for superconducting nanowire single-photon detectors. We experimentally test it against a bright-light attack, previously used to compromise security of quantum key distribution. Although our system detects continuous blinding, the detector is shown to be partially blindable and controllable by specially tailored sequences of bright pulses. Improvements to the countermeasure are suggested.
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Tiulina V, Iomdina E, Goltsman G, Seliverstov S, Sianosyan A, Teplyakova K, et al. UVB promotes the initiation of uveitic inflammatory and changes in thehydration of the cornea in vivo. Vol 9.; 2019.
Abstract: Recently, active research has been conducted in the field of terahertz (THz) scanning of human tissues for noninvasive determination of their hydration level, which haves hown high diagnostic efficiency of this technology in various pathological conditions. Recently, we have developed a laboratory model of the facility for monitoring the state of the water balance of the cornea using THz scanning in vivo, which opens up the possibility of applying this approach in ophthalmology. The aim of the work wasto compare the results of the THz scan of the cornea with its clinical changes using the example of an experimental model of the UV induced keratouveitis. Anexperimental study, which included a comprehensive assessment of clinical changes in the cornea of rabbits during keratouveitis induction, revealed a decrease in the stability of the tear film, pathological changes in the corneal epithelium and stroma, as well as its anatomical and optical parameters. Comparison of data obtained in the THz scan of the cornea with tears production, optical coherence tomography and confocal microscopy showed their consistency in all observation periods, which allows us to conclude that the developed laboratory setup works and the feasibility of further research to promote the corneal hydration evaluation technology in clinical practice. Acknowledgements: Research was funded by the RSF, grant number 161500255.
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Antipov S, Trifonov A, Krause S, Meledin D, Kaurova N, Rudzinski M, et al. Improved bandwidth of a 2 THz hot-electron bolometer heterodyne mixer fabricated on sapphire with a GaN buffer layer. Supercond Sci Technol. 2019;32(7):075003.
Abstract: We report on the signal-to-noise and gain bandwidth of a niobium nitride (NbN) hot-electron bolometer (HEB) mixer at 2 THz fabricated on a sapphire substrate with a GaN buffer layer. Two mixers with different DC properties and geometrical dimensions were studied and they demonstrated very close bandwidth performance. The signal-to-noise bandwidth is increased to 8 GHz in comparison to the previous results, obtained without a buffer-layer. The data were taken in a quasi-optical system with the use of the signal-to-noise method, which is close to the signal levels used in actual astrophysical observations. We find an increase of the gain bandwidth to 5 GHz. The results indicate that prior results obtained on a substrate of crystalline GaN can also be obtained on a conventional sapphire substrate with a few micron MOCVD-deposited GaN buffer-layer.
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Saveskul NA, Titova NA, Baeva EM, Semenov AV, Lubenchenko AV, Saha S, et al. Superconductivity behavior in epitaxial TiN films points at surface magnetic disorder [Internet].; 2019 [cited 2024 Jul 1].arXiv:1903.05009v3 [cond-mat.mtrl-sci]. Available from: https://arxiv.org/abs/1903.05009v3
Abstract: We analyze the evolution of the normal and superconducting electronic properties in epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of in the residual resistivity, which becomes dominated by diffusive surface scattering for d≤20nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such a high quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of ∼1012cm−2. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films.
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Tovpeko NA, Trifonov AV, Semenov AV, Antipov SV, Kaurova NS, Titova NA, et al. Bandwidth performance of a THz normal metal TiN bolometer-mixer. In: Proc. 30th Int. Symp. Space Terahertz Technol.; 2019. p. 102–3.
Abstract: We report on the bandwidth performance of the normal metal TiN bolometer-mixer on top of an Al 2 O 3 substrate, which is capable to operate in a wide range of bath temperatures from 77 K – 300 K. The choice of the combination TiN / Al 2 O 3 is related to an advanced heat transport between the film and the substrate in this pair and the sufficient temperature coefficient of resistance. The data were taken at 132.5 – 145.5 GHz with two BWOs as a signal and an LO source. Measurements were taken on TiN films of different thickness starting from 20 nm down to 5 nm coupled into a spiral Au antenna, which improves matching of incoming radiation with the thin TiN fim. Our experiments demonstrate effective heat coupling from a TiN thin film to an Al 2 O 3 substrate (111) boosting gain bandwidth (GB) of TiN bolometer up to 6 GHz for 5 nm thin film. Current results indicate weak temperature dependence of GB on the bath temperature of the TiN bolometer. Theoretical estimations of GB performance meet with experimental data for 5 nm thin TiN films.
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Kovaluyk V, Lazarenko P, Kozyukhin S, An P, Prokhodtsov A, Goltsman G, et al. Influence of the phase state of Ge2Sb2Te5 thin cover on the parameters of the optical waveguide structures [abstract]. In: Proc. Amorphous and Nanostructured Chalcogenides. Technical University of Moldova; 2019. p. 47–8.
Abstract: The fast switching time of Ge-Sb-Te thin films between amorphous and crystalline states initiated by laser beam as well as significant change of their optical properties and the preservation of metastable states for tens of years open wide perspectives for the application of these materials to fully optical devices [1], including high-speed optical memory [2]. Here we study optical properties of the Ge2Sb2Te5 (GST225) thin films integrated with on-chip silicon nitride O-ring resonator. The rib waveguide of the resonator was formed the first stage of e-beam lithography and subsequent reactive-ion etching. We used the second stage of e-beam lithography combining with lift-off method for the formation of GST225 active region on the resonator ring surface. The amorphous GST225 thin films were prepared by magnetron sputtering, and were capped by thin silicon oxide on their tops. The length of the GST225 active region varied from 0.1 to 20 μ m. Crystallization of amorphous thin films was carried out at the temperature of 400 °C for 30 minutes. Auger electron spectroscopy and transmission electron microscopy were used for studying composition and structure of investigated GST225thin films, respectively. It was observed that crystallization of amorphous GST225 film lead to a decrease of the optical power, transmitted through the waveguide. Comparison of the optical transmittance of O-ring resonators before and after the GST225 deposition allowed to identify the change in the Q-factor and the wavelength peak shift. This can be explained by the differences of the complex refractive indexes of GST225 thin films in the amorphous and crystalline states. From the measurement data, the GST225 effective refractive index was extracted depending on the ring waveguide width of the resonator for a telecommunication wavelength of 1550 nm.
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Tretyakov I, Svyatodukh S, Chumakova A, Perepelitsa A, Kaurova N, Shurakov A, et al. Room temperature silicon detector for IR range coated with Ag2S quantum dots. In: IRMMW-THz.; 2019.
Abstract: A silicon has been the chief technological semiconducting material of modern microelectronics and has had a strong influence on all aspects of society. Applications of Si-based optoelectronic devices are limited to the visible and near infrared ranges. The expansion of the Si absorption to shorter wavelengths of the infrared range is of considerable interest to optoelectronic applications. By creating impurity states in Si it is possible to cause sub-band gap photon absorption. Here, we present an elegant and effective technology of extending the photoresponse of towards the IR range. Our approach is based on the use of Ag 2 S quantum dots (QDs) planted on the surface of Si. The specific sensitivity of the Ag 2 S/Si heterostructure is 10 11 cm√HzW -1 at 1.55μm. Our findings open a path towards the future study and development of Si detectors for technological applications.
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