Seleznev VA, Divochiy AV, Vakhtomin YB, Morozov PV, Zolotov PI, Vasil'ev DD, et al. Superconducting detector of IR single-photons based on thin WSi films. In: J. Phys.: Conf. Ser. Vol 737.; 2016. 012032.
Abstract: We have developed the deposition technology of WSi thin films 4 to 9 nm thick with high temperature values of superconducting transition (Tc~4 K). Based on deposed films there were produced nanostructures with indicative planar sizes ~100 nm, and the research revealed that even on nanoscale the films possess of high critical temperature values of the superconducting transition (Tc~3.3-3.7 K) which certifies high quality and homogeneity of the films created. The first experiments on creating superconducting single-photon detectors showed that the detectors' SDE (system detection efficiency) with increasing bias current (I b) reaches a constant value of ~30% (for X=1.55 micron) defined by infrared radiation absorption by the superconducting structure. To enhance radiation absorption by the superconductor there were created detectors with cavity structures which demonstrated a practically constant value of quantum efficiency >65% for bias currents Ib>0.6-Ic. The minimal dark counts level (DC) made 1 s-1 limited with background noise. Hence WSi is the most promising material for creating single-photon detectors with record SDE/DC ratio and noise equivalent power (NEP).
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Moshkova M, Divochiy A, Morozov P, Vakhtomin Y, Antipov A, Zolotov P, et al. High-performance superconducting photon-number-resolving detectors with 86% system efficiency at telecom range. J Opt Soc Am B. 2019;36(3):B20.
Abstract: The use of improved fabrication technology, highly disordered NbN thin films, and intertwined section topology makes it possible to create high-performance photon-number-resolving superconducting single-photon detectors (PNR SSPDs) that are comparable to conventional single-element SSPDs at the telecom range. The developed four-section PNR SSPD has simultaneously an 86±3% system detection efficiency, 35 cps dark count rate, ∼2 ns dead time, and maximum 90 ps jitter. An investigation of the PNR SSPD’s detection efficiency for multiphoton events shows good uniformity across sections. As a result, such a PNR SSPD is a good candidate for retrieving the photon statistics for light sources and quantum key distribution systems.
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Zolotov P, Divochiy A, Vakhtomin Y, Seleznev V, Morozov P, Smirnov K. Superconducting single-photon detectors made of ultra-thin VN films. In: KnE Energy. Vol 3.; 2018. p. 83–9.
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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Smirnov K, Divochiy A, Vakhtomin Y, Morozov P, Zolotov P, Antipov A, et al. NbN single-photon detectors with saturated dependence of quantum efficiency. Supercond Sci Technol. 2018;31(3):035011 (1 to 8).
Abstract: The possibility of creating NbN superconducting single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized bias current was investigated. It was shown that the saturation increases for the detectors based on finer films with a lower value of Rs300/Rs20. The decreasing of Rs300/Rs20 was related to the increasing influence of quantum corrections to conductivity of superconductors and, in turn, to the decrease of the electron diffusion coefficient. The best samples have a constant value of system QE 94% at Ib/Ic ~ 0.8 and wavelength 1310 nm.
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Zolotov PI, Divochiy AV, Vakhtomin YB, Morozov PV, Seleznev VA, Smirnov KV. Development of high-effective superconducting single-photon detectors aimed for mid-IR spectrum range. In: J. Phys.: Conf. Ser. Vol 917.; 2017. 062037.
Abstract: We report on development of superconducting single-photon detectors (SSPD) with high intrinsic quantum efficiency in the wavelength range 1.31 – 3.3 μm. By optimization of the NbN film thickness and its compound, we managed to improve detection efficiency of the detectors in the range up to 3.3 μm. Optimized devices showed intrinsic quantum efficiencies as high as 10% at mid-IR range.
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