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Korneeva Y, Florya I, Vdovichev S, Moshkova M, Simonov N, Kaurova N, et al. Comparison of hot spot formation in nbn and mon thin superconducting films after photon absorption. IEEE Trans Appl Supercond. 2017;27(4):1–4.
Abstract: In superconducting single-photon detectors (SSPD), the efficiency of local suppression of superconductivity and hotspot formation is controlled by diffusivity and electron-phonon interaction time. Here, we selected a material, 3.6-nm-thick MoNx film, which features diffusivity close to those of NbN traditionally used for SSPD fabrication, but with electron-phonon interaction time an order of magnitude larger. In MoN ∞ detectors, we study the dependence of detection efficiency on bias current, photon energy, and strip width, and compare it with NbN SSPD. We observe nonlinear current-energy dependence in MoNx SSPD and more pronounced plateaus in dependences of detection efficiency on bias current, which we attribute to longer electron-phonon interaction time.
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Vodolazov DY, Manova NN, Korneeva YP, Korneev AA. Timing jitter in NbN superconducting microstrip single-photon detector. Phys Rev Applied. 2020;14(4):044041 (1 to 8).
Abstract: We experimentally study timing jitter of single-photon detection by NbN superconducting strips with width w ranging from 190 nm to 3μm. We find that timing jitter of both narrow (190 nm) and micron-wide strips is about 40 ps at currents where internal detection efficiency η saturates and it is close to our instrumental jitter. We also calculate intrinsic timing jitter in wide strips using the modified time-dependent Ginzburg-Landau equation coupled with a two-temperature model. We find that with increasing width the intrinsic timing jitter increases and the effect is most considerable at currents where a rapid growth of η changes to saturation. We relate it with complicated vortex and antivortex dynamics, which depends on a photon’s absorption site across the strip and its width. The model also predicts that at current close to depairing current the intrinsic timing jitter of a wide strip could be about ℏ/kBTc (Tc is a critical temperature of superconductor), i.e., the same as for a narrow strip.
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Semenov AV, Devyatov IA, Korneev AA, Smirnov KV, Goltsman GN, Melnikov AP. Derivation of expression for thermodynamic potential of “dirty” superconductor. Rus J Radio Electron. 2012;(4).
Abstract: We derive a formula for thermodynamic potential of dirty superconductor which express it via isotropic quasiclassical Green functions of Usadel theory. Our result allows unify description of dynamic processes and fluctuations in superconducting nano-electronic devices.
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Korneeva Y, Florya I, Semenov A, Korneev A, Goltsman G. New generation of nanowire NbN superconducting single-photon detector for mid-infrared. IEEE Trans Appl Supercond. 2011;21(3):323–6.
Abstract: We present a break-through approach to mid-infrared single-photon detection based on nanowire NbN superconducting single-photon detectors (SSPD). Although SSPD became a mature technology for telecom wavelengths (1.3-1.55 μm) its further expansion to mid-infrared wavelength was hampered by low sensitivity above 2 μm. We managed to overcome this limit by reducing the nanowire width to 50 nm, while retaining high superconducting properties and connecting the wires in parallel to produce a voltage response of sufficient magnitude. The new device exhibits 10 times better quantum efficiency at 3.5 μm wavelength than the “standard” SSPD.
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Glejm AV, Anisimov AA, Asnis LN, Vakhtomin YB, Divochiy AV, Egorov VI, et al. Quantum key distribution in an optical fiber at distances of up to 200 km and a bit rate of 180 bit/s. Bulletin of the Russian Academy of Sciences. Physics. 2014;78(3):171–5.
Abstract: An experimental demonstration of a subcarrier-wave quantum cryptography system with superconducting single-photon detectors (SSPDs) that distributes a secure key in a single-mode fiber at distance of 25 km with a bit rate of 800 kbit/s, a distance of 100 km with a bit rate of 19 kbit/s, and a distance of 200 km with a bit rate of 0.18 kbit/s is described.
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Korneev AA, Korneeva YP, Mikhailov MY, Pershin YP, Semenov AV, Vodolazov DY, et al. Characterization of MoSi superconducting single-photon detectors in the magnetic field. IEEE Trans Appl Supercond. 2015;25(3):2200504 (1 to 4).
Abstract: We investigate the response mechanism of nanowire superconducting single-photon detectors (SSPDs) made of amorphous MoxSi1-x. We study the dependence of photon count and dark count rates on bias current in magnetic fields up to 113 mT at 1.7 K temperature. The observed behavior of photon counts is similar to the one recently observed in NbN SSPDs. Our results show that the detecting mechanism of relatively high-energy photons does not involve the vortex penetration from the edges of the film, and on the contrary, the detecting mechanism of low-energy photons probably involves the vortex penetration from the film edges.
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Korneev A, Korneeva Y, Manova N, Larionov P, Divochiy A, Semenov A, et al. Recent nanowire superconducting single-photon detector optimization for practical applications. IEEE Trans Appl Supercond. 2013;23(3):2201204 (1 to 4).
Abstract: In this paper, we present our approaches to the development of fiber-coupled superconducting single photon detectors with enhanced photon absorption. For such devices we have measured detection efficiency in wavelength range from 500 to 2000 nm. The best fiber coupled devices exhibit detection efficiency of 44.5% at 1310 nm wavelength and 35.5% at 1550 nm at 10 dark counts per second.
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Florya IN, Korneeva YP, Mikhailov MY, Devizenko AY, Korneev AA, Goltsman GN. Photon counting statistics of superconducting single-photon detectors made of a three-layer WSi film. Low Temp Phys. 2018;44(3):221–5.
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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Korneeva Y, Sidorova M, Semenov A, Krasnosvobodtsev S, Mitsen K, Korneev A, et al. Comparison of hot-spot formation in NbC and NbN single-photon detectors. IEEE Trans Appl Supercond. 2016;26(3):1–4.
Abstract: We report an experimental investigation of the hot-spot evolution in superconducting single-photon detectors made of disordered superconducting materials with different diffusivity and energy downconversion time values, i.e., 33-nm-thick NbN and 23-nm-thick NbC films. We have demonstrated that, in NbC film, only 405-nm photons produce sufficiently large hot spot to trigger a single-photon response. The dependence of detection efficiency on bias current for 405-nm photons in NbC is similar to that for 3400-nm photons in NbN. In NbC, large diffusivity and downconversion time result in 1-D critical current suppression profile compared with the usual 2-D profile in NbN.
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Lusche R, Semenov A, Il'in K, Korneeva Y, Trifonov A, Korneev A, et al. Effect of the wire width and magnetic field on the intrinsic detection efficiency of superconducting nanowire single-photon detectors. IEEE Trans Appl Supercond. 2013;23(3):2200205.
Abstract: We present thorough measurements of the intrinsic detection efficiency in the wavelength range from 350 to 2500 nm for meander-type TaN and NbN superconducting nanowire single-photon detectors with different widths of the nanowire. The width varied from 70 nm to 130 nm. The open-beam configuration allowed us to accurately normalize measured spectra and to extract the intrinsic detection efficiency. For detectors from both materials the intrinsic detection efficiency at short wavelengths amounts at 100% and gradually decreases at wavelengths larger than the specific cut-off wavelengths, which decreases with the width of the nanowire. Furthermore, we show that applying weak magnetic fields perpendicular to the meander plane decreases the smallest detectable photon flux.
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