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Gershenzon, Ye. M.; Goltsman, G. N.; Yelantyev, A. I.; Petrova, Ye. B.; Ptitsina, N. G.; Filatov, V. S. |
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Lecture demonstrations of properties of superconductors and liquid helium |
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1987 |
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USSR Rept Phys. Math. JPRS UPM |
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USSR Rept Phys. Math. JPRS UPM |
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24 |
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7 |
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51 |
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demonstrations, lections |
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New demonstrations for low temperature physics courses are described. Two transparent Dewar vacuum flasks fitting one inside the other with the external flask for nitrogen and the internal flask for helium are used. The helium temperature can be regulated in the 4.2 to 1.6 K range and the effects of reducing helium to the superfluid state at 2.17 K can be shown: boiling abruptly stops and superfluid flow appears. In order to show the electric and magnetic characteristics of superconductivity, a superconducting NbTi solenoid containing nonsuperconducting wire and germanium and superconducting Nb materials with different critical temperatures is placed in the helium refrigerant vessel. The fall of the resistance at the critical temperatures can be shown. In order to show magnetic field and superconductive current flow properties a shunt of superconductive material is connected in parallel to the coil and is enclosed in a teflon container with a heater which can vary its temperature. When it is heated and not superconductive, magnetic field effects can be demonstrated and when it is unheated and superconducting a continuous current can be demonstrated. |
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1704 |
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Krause, S.; Mityashkin, V.; Antipov, S.; Gol’tsman, G.; Meledin, D.; Desmaris, V.; Belitsky, V.; Rudziński, M. |
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Title |
Reduction of phonon escape time for nbn hot electron bolometers by using gan buffer layers |
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Journal Article |
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2017 |
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IEEE Trans. Terahertz Sci. Technol. |
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IEEE Trans. Terahertz Sci. Technol. |
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7 |
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1 |
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53-59 |
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NbN HEB mixer |
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In this paper, we investigated the influence of the GaN buffer layer on the phonon escape time of phonon-cooled hot electron bolometers (HEBs) based on NbN material and compared our findings to conventionally employed Si substrate. The presented experimental setup and operation of the HEB close to the critical temperature of the NbN film allowed for the extraction of phonon escape time in a simplified manner. Two independent experiments were performed at GARD/Chalmers and MSPU on a similar experimental setup at frequencies of approximately 180 and 140 GHz, respectively, and have shown reproducible and consistent results. By fitting the normalized IF measurement data to the heat balance equations, the escape time as a fitting parameter has been deduced and amounts to 45 ps for the HEB based on Si substrate as in contrast to a significantly reduced escape time of 18 ps for the HEB utilizing the GaN buffer layer under the assumption that no additional electron diffusion has taken place. This study indicates a high phonon transmissivity of the NbN-to-GaN interface and a prospective increase of IF bandwidth for HEB made of NbN on GaN buffer layers, which is desirable for future THz HEB heterodyne receivers. |
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2156-3446 |
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1330 |
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Gershenzon, E. M.; Gol'tsman, G. N. |
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Transitions of electrons between excited states of donors in germanium |
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1971 |
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JETP Lett. |
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JETP Lett. |
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14 |
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2 |
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63-65 |
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Ge, donors, excited states |
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1740 |
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Гольцман, Г. Н.; Разумовская, И. В.; Окунев, О. В; Чулкова, Г. М.; Корнеев, А. А.; Финкель, М. И.; Масленников, С. Н.; Семенов, А. В.; Александров, В. Н. |
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Сборник программ учебных дисциплин профессионального цикла подготовки магистров и бакалавров по направлению «Физика» |
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2011 |
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Прометей |
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Прометей |
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67 |
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Учебное пособие |
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RPLAB @ gujma @ |
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717 |
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Korneev, A.; Finkel, M.; Maslennikov, S.; Korneeva, Yu.; Florya, I.; Tarkhov, M.; Elezov, M.; Ryabchun, S.; Tretyakov, I.; Isupova, A.; Voronov, B.; Goltsman, G. |
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Superconducting NbN terahertz detectors and infrared photon counters |
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2010 |
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Вестник НГУ. Серия: физ. |
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Вестник НГУ. Серия: физ. |
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5 |
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4 |
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68-72 |
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HEB; HEB mixer |
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We present our recent achievements in the development of sensitive and ultrafast thin-film superconducting sensors: hot-electron bolometers (HEB), HEB-mixers for terahertz range and infrared single-photon counters. These sensors have already demonstrated a performance that makes them devices-of-choice for many terahertz and optical applications. Keywords: Hot electron bolometer mixers, infrared single-photon detectors, superconducting device fabrication, superconducting NbN films. |
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1818-7994 |
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УДК 538.9 |
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RPLAB @ gujma @ |
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708 |
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Neroev, V. V.; Iomdina, E. N.; Khandzhyan, A. T.; Khodzhabekyan, N. V.; Sengaeva, M. D.; Ivanova, A. V.; Seliverstov, S. V.; Teplyakova, K. O.; Goltsman, G. N. |
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Experimental study of the effect of corneal hydration and its biomechanical properties on the results of photorefractive keratectomy |
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2021 |
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Vestn. Oftalmol. |
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Vestn. Oftalmol. |
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137 |
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3 |
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68-75 |
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THz scanning, cornea, photorefractive keratectomy, medicine |
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Water content in the cornea may affect the outcome of its excimer laser ablation, especially in presbyopic patients with myopic refraction. This hypothesis can be tested by scanning the cornea in the terahertz (THz) range to determine its hydration level.
Purpose: To study the effect of hydration of the cornea determined by non-contact THz scanning and its biomechanical parameters on the results of photorefractive keratectomy (PRK) in an experiment.
Material and methods: PRK was performed using the Nidek EC-5000 QUEST excimer laser on 8 rabbit eyes. Corneal hydration was evaluated by determining the reflection coefficient (RC) in the THz electromagnetic radiation range before PRK, after 3-5 days, and after 1, 2, 3, and 4 months. Clinical examination included autorefractometry, assessment of corneal thickness and other anatomical and optical parameters of the anterior eye segment (Galilei G6, Ziemer Ophthalmic Systems AG 6.0.2, Switzerland), measurement of corneal hysteresis (CH) and corneal resistance factor (CRF) using the Ocular Response Analyzer (ORA; Reichert, USA), as well as tear production (Schirmer test).
Results: The initial water content in the cornea has a significant effect on the thickness of the removed layer, i.e. on the PRK effect, with correlation coefficient of Rs= -0.976 (p<0.01). The correlation between CH and the ablation depth is less pronounced (Rs=0.643), and CRF had no correlation with it (Rs= -0.089). Biomechanical indicators of the cornea depend on its hydration: changes in CH and CRF after excimer laser ablation qualitatively coincide with changes in RC, the correlation coefficient between RC and the initial value of CH is R= -0.619 (moderate negative correlation).
Conclusion: THz scanning is an effective non-contact technology for monitoring corneal hydration level. The mismatch of the hypoeffect of keratorefractive excimer laser intervention planned for patients with presbyopia with the actual outcome can be caused by individual decrease in the initial water content in the cornea. |
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Russian |
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1794 |
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Ожегов, Р.В.; Горшков, К.Н.; Окунев, О.В.; Гольцман, Г.Н. |
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Сверхпроводниковый смеситель на эффекте электронного разогрева как элемент матрицы системы построения тепловых изображений |
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2010 |
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Письма в Журнал технической физики |
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Письма в ЖТФ |
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36 |
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21 |
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70-78 |
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Исследована возможность использования матрицы чувствительных элементов на гиперполусферической линзе диаметром 12 mm в тепловизоре терагерцевого диапазона частот. Получены размеры области на линзе, приемлемой для расположения матрицы, в которой шумовая температура приемника меняется в пределах 16% от средней. Диаметр этой области составил 3.3% диаметра линзы.Получены отклонения основного лепестка диаграммы направленности, которые составили ±1.25â—<a6> от направления с оптимальным положением смесителя. Флуктуационная чувствительность приемника в эксперименте составила 0.5 K на частоте 300 GHz. |
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RPLAB @ gujma @ |
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704 |
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Korneev, A.; Korneeva, Y.; Florya, I.; Voronov, B.; Goltsman, G. |
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NbN nanowire superconducting single-photon detector for mid-infrared |
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2012 |
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Phys. Procedia |
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Phys. Procedia |
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36 |
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72-76 |
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NbN SSPD, SNSPD |
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Superconducting single-photon detectors (SSPD) is typically 100 nm-wide supercondiucting strip in a shape of meander made of 4-nm-thick film. To reduce response time and increase voltage response a parallel connection of the strips was proposed. Recently we demonstrated that reduction of the strip width improves the quantum effciency of such a detector at wavelengths longer than 1.5 μm. Being encourage by this progress in quantum effciency we improved the fabrication process and made parallel-wire SSPD with 40-nm-wide strips covering total area of 10 μm x 10 μm. In this paper we present the results of the characterization of such a parallel-wire SSPD at 10.6 μm wavelength and demonstrate linear dependence of the count rate on the light power as it should be in case of single-photon response. |
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1875-3892 |
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1382 |
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Третьяков, И.В.; Рябчун, С.А.; Каурова, Н.С.; Ларионов, П.А.; Лобастова, А.А.; Воронов, Б.М.; Финкель, М.И.; Гольцман, Г.Н. |
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Оптимальная поглощенная мощность гетеродина для терагерцового сверхпроводникового NbN смесителя на электронном разогреве |
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2010 |
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Письма в Журнал технической физики |
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Письма в ЖТФ |
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36 |
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23 |
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78-84 |
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Представлены результаты измерений поглощенной мощности гетеродина малошумящим широкополосным смесителем на эффекте электронного разогрева в резистивном состоянии сверхпроводниковой ультратонкой пленки NbN. Оптимальная поглощенная мощность гетеродина составила около 100 nW на частоте 2.5 THz. |
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Расулова, Г.К.; Брунков, П.Н.; Пентин, И.В.; Ковалюк, В.В.; Горшков, К.Н.; Казаков, А.Ю.; Иванов, С.Ю.; Егоров, А.Ю.; Саксеев, Д.А.; Конников, С.Г. |
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Взаимная синхронизация двух связанных генераторов автоколебаний на основе сверхрешеток GaAs/AlGaAs |
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2011 |
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Журнал технической физики |
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ЖТФ |
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81 |
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6 |
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80-86 |
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Проведено исследование взаимодействия генераторов автоколебаний на основе 30-периодной слабосвязанной сверхрешетки GaAs/AlGaAs. Воздействие одного генератора автоколебаний на другой осуществлялось при заданном постоянном смещении в отсутствие в одном из них генерации автономных колебаний. Показано, что вынужденные колебания в захватывающем генераторе возникают из-за возбуждения колебаний в системе связанных осцилляторов, образующих границу электрополевого домена на частоте одной из высших гармоник вынуждающего колебания. |
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