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Titova N, Kardakova A, Tovpeko N, Ryabchun S, Mandal S, Morozov D, et al. Superconducting diamond films as perspective material for direct THz detectors [abstract]. In: Proc. 28th Int. Symp. Space Terahertz Technol.; 2017. 82.
Abstract: Superconducting films with a high resistivity in the normal state have established themselves as the best materials for direct THz radiation sensors, such as kinetic inductance detectors (KIDs) [1] and hot electron bolometers (nano-HEBs) [2]. The primary characteristics of the future instrument such as the sensitivity and the response time are determined by the material parameters such as the electron-phonon (e-ph) interaction time, the electron density and the resistivity of the material. For direct detectors, such as KIDs and nano-HEBs, to provide a high sensitivity and low noise one prefer materials with long e-ph relaxation times and low values of the electron density. As a potential material for THz radiation detection we have studied superconducting diamond films. A significant interest to diamond for the development of electronic devices is due to the evolution of its properties with the boron dopant concentration. At a high boron doping concentration, n B ~5·10 20 cm -3 , diamond has been reported to become a superconducting with T c depending on the doping level. Our previous study of energy relaxation in single-crystalline boron-doped diamond films epitaxially grown on a diamond shows a remarkably slow energy-relaxation at low temperatures. The electron-phonon cooling time varies from 400 ns to 700 ns over the temperature range 2.2 K to 1.7 K [3]. In superconducting materials such as Al and TiN, traditionally used in KIDs, the e-ph cooling times at 1.7 K correspond to ~20 ns [4] and ~100 ns [5], correspondingly. Such a noticeable slow e-ph relaxation in boron-doped diamond, in combination with a low value of carrier density (~10 21 cm -3 ) in comparison with typical metals (~10 23 cm -3 ) and a high normal state resistivity (~1500 μΩ·cm) confirms a potential of superconducting diamond for superconducting bolometers and resonator detectors. However, the price and the small substrate growth are of single crystal diamond limit practical applications of homoepitaxial diamond films. As an alternative way with more convenient technology, one can employ heteroepitaxial diamond films grown on large-size Si substrates. Here we report about measurements of e-ph cooling times in superconducting diamond grown on silicon substrate and discuss our expectations about the applicability of boron-doped diamond films to superconducting detectors. Our estimation of limit value of noise-equivalent power (NEP) and the energy resolution of bolometer made from superconducting diamond is order 10 -17 W/Hz 1/2 at 2 K and the energy resolution is of 0.1 eV that corresponds to counting single-photon up to 15 um. The estimation was obtained by using the film thickness of 70 nm and ρ ~ 1500 μΩ·cm, and the planar dimensions that are chosen to couple bolometer with 75 Ω log-spiral antenna. Although the value of NEP is far yet from what might like to have for certain astronomical applications, we believe that it can be improved by a suitable fabrication process. Also the direct detectors, based on superconducting diamond, will offer low noise performance at about 2 K, a temperature provided by inexpensive close-cycle refrigerators, which provides another practical advantage of development and application of these devices. [1] P.K. Day, et. al, Nature, 425, 817, 2003. [2] J. Wei, et al, Nature Nanotech., 3, 496, 2008. [3] A. Kardakova, et al, Phys. Rev. B, 93, 064506, 2016. [4] P. Santhanam and D. Prober, Phys. Rev. B, 29, 3733, 1984 [5] A. Kardakova, et al, Appl. Phys. Lett, vol. 103, p. 252602, 2013.
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Lobanov Y, Shcherbatenko M, Semenov A, Kovalyuk V, Kahl O, Ferrari S, et al. Superconducting nanowire single photon detector for coherent detection of weak signals. IEEE Trans Appl Supercond. 2017;27(4):1–5.
Abstract: Traditional photon detectors are operated in the direct detection mode, counting incident photons with a known quantum efficiency. Here, we have investigated a superconducting nanowire single photon detector (SNSPD) operated as a photon counting mixer at telecommunication wavelength around 1.5 μm. This regime of operation combines excellent sensitivity of a photon counting detector with excellent spectral resolution given by the heterodyne technique. Advantageously, we have found that low local oscillator (LO) power of the order of hundreds of femtowatts to a few picowatts is sufficient for clear observation of the incident test signal with the sensitivity approaching the quantum limit. With further optimization, the required LO power could be significantly reduced, which is promising for many practical applications, such as the development of receiver matrices or recording ultralow signals at a level of less-than-one-photon per second. In addition to a traditional NbN-based SNSPD operated with normal incidence coupling, we also use detectors with a travelling wave geometry, where a NbN nanowire is placed on the top of a Si 3 N 4 nanophotonic waveguide. This approach is fully scalable and a large number of devices could be integrated on a single chip.
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Klapwijk TM, Semenov AV. Engineering physics of superconducting hot-electron bolometer mixers. IEEE Trans THz Sci Technol. 2017;7(6):627–48.
Abstract: Superconducting hot-electron bolometers are presently the best performing mixing devices for the frequency range beyond 1.2 THz, where good-quality superconductor-insulator-superconductor devices do not exist. Their physical appearance is very simple: an antenna consisting of a normal metal, sometimes a normal-metal-superconductor bilayer, connected to a thin film of a narrow short superconductor with a high resistivity in the normal state. The device is brought into an optimal operating regime by applying a dc current and a certain amount of local-oscillator power. Despite this technological simplicity, its operation has found to be controlled by many different aspects of superconductivity, all occurring simultaneously. A core ingredient is the understanding that there are two sources of resistance in a superconductor: a charge-conversion resistance occurring at a normal-metal-superconductor interface and a resistance due to time-dependent changes of the superconducting phase. The latter is responsible for the actual mixing process in a nonuniform superconducting environment set up by the bias conditions and the geometry. The present understanding indicates that further improvement needs to be found in the use of other materials with a faster energy relaxation rate. Meanwhile, several empirical parameters have become physically meaningful indicators of the devices, which will facilitate the technological developments.
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Lobanov YV, Shcherbatenko ML, Semenov AV, Kovalyuk VV, Korneev AA, Goltsman GN, et al. Heterodyne spectroscopy with superconducting single-photon detector. In: EPJ Web Conf. Vol 132.; 2017. 01005.
Abstract: We demonstrate successful operation of a Superconducting Single Photon Detector (SSPD) as the core element in a heterodyne receiver. Irradiating the SSPD by both a local oscillator power and signal power simultaneously, we observed beat signal at the intermediate frequency of a few MHz. Gain bandwidth was found to coincide with the detector single pulse width, where the latter depends on the detector kinetic inductance, determined by the superconducting nanowire length.
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Titova N, Kardakova AI, Tovpeko N, Ryabchun S, Mandal S, Morozov D, et al. Slow electron–phonon cooling in superconducting diamond films. IEEE Trans Appl Supercond. 2017;27(4):1–4.
Abstract: We have measured the electron-phonon energy-relaxation time, τ eph , in superconducting boron-doped diamond films grown on silicon substrate by chemical vapor deposition. The observed electron-phonon cooling times vary from 160 ns at 2.70 K to 410 ns at 1.8 K following a T -2-dependence. The data are consistent with the values of τ eph previously reported for single-crystal boron-doped diamond films epitaxially grown on diamond substrate. Such a noticeable slow electron-phonon relaxation in boron-doped diamond, in combination with a high normal-state resistivity, confirms a potential of superconducting diamond for ultrasensitive superconducting bolometers.
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Vorobyov VV, Kazakov AY, Soshenko VV, Korneev AA, Shalaginov MY, Bolshedvorskii SV, et al. Superconducting detector for visible and near-infrared quantum emitters [Invited]. Opt Mater Express. 2017;7(2):513–26.
Abstract: Further development of quantum emitter based communication and sensing applications intrinsically depends on the availability of robust single-photon detectors. Here, we demonstrate a new generation of superconducting single-photon detectors specifically optimized for the 500–1100 nm wavelength range, which overlaps with the emission spectrum of many interesting solid-state atom-like systems, such as nitrogen-vacancy and silicon-vacancy centers in diamond. The fabricated detectors have a wide dynamic range (up to 350 million counts per second), low dark count rate (down to 0.1 counts per second), excellent jitter (62 ps), and the possibility of on-chip integration with a quantum emitter. In addition to performance characterization, we tested the detectors in real experimental conditions involving nanodiamond nitrogen-vacancy emitters enhanced by a hyperbolic metamaterial.
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Столяров АВ. Программирование. Введение в профессию. Том 3. Системы и сети. Москва; 2017.
Abstract: В третий том книги «Программирование: введение в профессию» вошли части V–VIII. В части V рассматриваются системные вызовы для ввода-вывода, управление процессами, механизмы взаимодействия процессов, такие как сигналы и каналы, а также понятие терминала и связанные с ним явления, в том числе сеансы и группы процессов, виртуальные терминалы, управление дисциплиной линии. Часть VI посвящена компьютерным сетям; даётся небольшой обзор протоколов, используемых в сети Интернет, рассмотрена подсистема сокетов и событийно-ориентированное построение серверных программ. В части VII рассматриваются вопросы, связанные с разделяемыми данными, критические секции, взаимоисключение; даются базовые сведения о библиотеке pthread. Часть VIII содержит ряд сведений о внутреннем устройстве операционной системы; в частности, рассматриваются различные модели виртуальной памяти, подсистема ввода-вывода и т.п.
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Столяров АВ. Программирование. Введение в профессию. Примеры программ.; 2017.
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Wördenweber R, Moshchalkov V, Bending S, Tafuri F, editors. Superconductors at the nanoscale. From basic research to applications. Berlin/Boston: Walter de Gruyter GmbH; 2017.
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Seliverstov SV, Rusova AA, Kaurova NS, Voronov BM, Goltsman GN. AC-biased superconducting NbN hot-electron bolometer for frequency-domain multiplexing. In: Proc. 28th Int. Symp. Space Terahertz Technol.; 2017. p. 120–2.
Abstract: We present the results of characterization of fast and sensitive superconducting antenna-coupled THz direct detector based on NbN hot-electron bolometer (HEB) with AC-bias. We discuss the possibility of implementation of the AC-bias for design the readout system from the multi-element arrays of HEBs using standard technique of frequency-domain multiplexing. We demonstrate experimentally that this approach does not lead to significant deterioration of the HEB sensitivity compared with the value obtained for the same detector with DC- bias. Results of a numerical calculations of the HEB responsivity at AC-bias are in a good agreement with the experiment.
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