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Florya, I. N., Korneeva, Y. P., Mikhailov, M. Y., Devizenko, A. Y., Korneev, A. A., & Goltsman, G. N. (2018). Photon counting statistics of superconducting single-photon detectors made of a three-layer WSi film. Low Temp. Phys., 44(3), 221–225.
Abstract: Superconducting nanowire single-photon detectors (SNSPD) are used in quantum optics when record-breaking time resolution, high speed, and exceptionally low levels of dark counts (false readings) are required. Their detection efficiency is limited, however, by the absorption coefficient of the ultrathin superconducting film for the detected radiation. One possible way of increasing the detector absorption without limiting its broadband response is to make a detector in the form of several vertically stacked layers and connect them in parallel. For the first time we have studied single-photon detection in a multilayer structure consisting of three superconducting layers of amorphous tungsten silicide (WSi) separated by thin layers of amorphous silicon. Two operating modes of the detector are illustrated: an avalanche regime and an arm-trigger regime. A shift in these modes occurs at currents of ∼0.5–0.6 times the critical current of the detector.
This work was supported by technical task No. 88 for scientific research at the National Research University “Higher School of Economics,” Grant No. 14.V25.31.0007 from the Ministry of Education and Science of Russia, and the work of G. N. Goltsman was supported by task No. 3.7328.2017/VU of the Ministry of Education and Science of Russia.
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Iomdina, E. N., Seliverstov, S. V., Sianosyan, A. A., Teplyakova, K. O., Rusova, A. A., & Goltsman, G. N. (2018). Terahertz scanning for evaluation of corneal and scleral hydration. STM, 10(4), 143–149.
Abstract: The aim of the investigation was to study the prospects of using continuous THz scanning of the cornea and the sclera to determine water concentration in these tissues and on the basis of the obtained data to develop the experimental installation for monitoring corneal and scleral hydration degree.Materials and Methods. To evaluate corneal and scleral transmittance and reflectance spectra in the THz range, the developed experimental installations were used to study 3 rabbit corneas and 3 scleras, 2 whole rabbit eyes, and 3 human scleras. Besides, two rabbit eyes were studied in vivo prior to keratorefractive surgery as well as 10 and 21 days following the surgery (LASIK).Results. There have been created novel experimental installations enabling in vitro evaluation of frequency dependence of corneal and scleral transmittance coefficients and reflectance coefficients on water percentage in the THz range. Decrease in corneal water content by 1% was found to lead to reliably established decrease in the reflected signal by 13%. The reflectance spectrum of the whole rabbit eye was measured in the range of 0.13–0.32 THz. The study revealed the differences between the indices of rabbit cornea and sclera, as well as rabbit and human sclera. There was developed a laboratory model of the installation for in vivo evaluation of corneal and scleral hydration using THz radiation.Conclusion. The preliminary findings show that the proposed technique based on the use of continuous THz radiation can be employed to create a device for noninvasive control of corneal and scleral hydration.
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Tretyakov, I., Kaurova, N., Voronov, B. M., & Goltsman, G. N. (2018). About effect of the temperature operating conditions on the noise temperature and noise bandwidth of the terahertz range NbN hot-electron bolometers. In Proc. 29th Int. Symp. Space Terahertz Technol. (113).
Abstract: Results of an experimental study of the noise temperature (Tn) and noise bandwidth (NBW) of the superconductor NbN hot-electron bolometer (HEB) mixer as a function of its temperature (Tb) and NbN bridge length are presented. It was determined that the NBW of the mixer is significantly wider at temperatures close to the critical ones (Tc) than are values measured at 4.2 K. The NBW of the mixer measured at the heterodyne frequency of 2.5 THz at temperature Tb close to Tc was ~13 GHz, as compared with 6 GHz at Tb = 4.2 K. This experiment clearly demonstrates the limitation of the thermal flow from the NbN bridge at Tb ≪ Tc for mixers manufactured by the in situ technique. This limitation is close in its nature to the Andreev reflection on the superconductor/metal boundary. In this case, the noise temperature of the studied mixer increased from 1100 to 3800 K.
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Zolotov, P., Divochiy, A., Vakhtomin, Y., Seleznev, V., Morozov, P., & Smirnov, K. (2018). Superconducting single-photon detectors made of ultra-thin VN films. In KnE Energy (Vol. 3, pp. 83–89).
Abstract: We optimized technology of thin VN films deposition in order to study VN-based superconducting single-photon detectors. Investigation of the main VN film parameters showed that this material has lower resistivity compared to commonly used NbN. Fabricated from obtained films devices showed 100% intrinsic detection efficiency at 900 nm, at the temperature of 1.7 K starting with the bias current of 0.7·I
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Золотов, Ф. И., Дивочий, А. В., Вахтомин, Ю. Б., Пентин, И. В., Морозов, П. В., Селезнев, В. А., et al. (2018). Применение тонких сверхпроводниковых пленок нитрида ванадия для изготовления счетчиков одиночных ИК-фотонов. In Сборн. науч. труд. VII международн. конф. по фотонике и информац. опт. (pp. 60–61).
Abstract: Получены первые результаты по применению сверхпроводниковых пленок нитрида ванадия (VN) для детекторов одиночных фотонов ИК-диапазона. Изучение сверхпроводниковых однофотонных детекторов (SSPD), изготовленных на основе ультратонких (~5 нм) пленок VN, показало возможность создания устройств с близкой к насыщению зависимостью квантовой эффективности от тока смещения детекторов в телекоммуникационном диапазоне длин волн. Также нами были исследованы кинетическая индуктивность изготовленных структур с различной длиной сверхпроводниковой полоски и времена релаксации электронов в тонких сверхпроводниковых пленках VN.
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