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Korneev A, Kovalyuk V, An P, Golikov A, Zubkova E, Ferrari S, et al. Superconducting single-photon detector for integrated waveguide spectrometer. In: EPJ Web Conf. Vol 190.; 2018. 04009.
Abstract: We present our recent achievements in the development of an on-chip spectrometer consisting of arrayed waveguide grating made of Si3N4 waveguides and NbN superconducting single-photon detector.
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Baeva EM, Sidorova MV, Korneev AA, Smirnov KV, Divochy AV, Morozov PV, et al. Thermal properties of NbN single-photon detectors. Phys Rev Applied. 2018;10(6):064063 (1 to 8).
Abstract: We investigate thermal properties of a NbN single-photon detector capable of unit internal detection efficiency. Using an independent calibration of the coupling losses, we determine the absolute optical power absorbed by the NbN film and, via resistive superconductor thermometry, the temperature dependence of the thermal resistance Z(T) of the NbN film. In principle, this approach permits simultaneous measurement of the electron-phonon and phonon-escape contributions to the energy relaxation, which in our case is ambiguous because of the similar temperature dependencies. We analyze Z(T) with a two-temperature model and impose an upper bound on the ratio of electron and phonon heat capacities in NbN, which is surprisingly close to a recent theoretical lower bound for the same quantity in similar devices.
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Zolotov PI, Divochiy AV, Vakhtomin YB, Lubenchenko AV, Morozov PV, Shurkaeva IV, et al. Influence of sputtering parameters on the main characteristics of ultra-thin vanadium nitride films. In: J. Phys.: Conf. Ser. Vol 1124.; 2018. 051030.
Abstract: We researched the relation between deposition and ultra-thin VN films parameters. To conduct the experimental study we varied substrate temperature, Ar and N2 partial pressures and deposition rate. The study allowed us to obtain the films with close to the bulk values transition temperatures and implement such samples in order to fabricate superconducting single-photon detectors.
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Romanov NR, Zolotov PI, Vakhtomin YB, Divochiy AV, Smirnov KV. Electron diffusivity measurements of VN superconducting single-photon detectors. In: J. Phys.: Conf. Ser. Vol 1124.; 2018. 051032.
Abstract: The research of ultrathin vanadium nitride (VN) films as a promising candidate for superconducting single-photon detectors (SSPD) is presented. The electron diffusivity measurements are performed for such devices. Devices that were fabricated out from 9.9 nm films had diffusivity coefficient of 0.41 cm2/s and from 5.4 nm – 0.54 cm2/s. Obtained values are similar to other typical SSPD materials. The diffusivity that increases along with decreasing of the film thickness is expected to allow fabrication of the devices with improved characteristics. Fabricated VN SSPDs showed prominent single-photon response in the range 0.9-1.55 µm.
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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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Zolotov P, Divochiy A, Vakhtomin Y, Moshkova M, Morozov P, Seleznev V, et al. Photon-number-resolving SSPDs with system detection efficiency over 50% at telecom range. In: Proc. AIP Conf. Vol 1936.; 2018. 020019.
Abstract: We used technology of making high-efficiency superconducting single-photon detectors as a basis for improvement of photon-number-resolving devices. By adding optical cavity and using an improved NbN superconducting film, we enhanced previously reported system detection efficiency at telecom range for such detectors. Our results show that implementation of optical cavity helps to develop four-section device with quantum efficiency over 50% at 1.55 µm. Performed experimental studies of detecting multi-photon optical pulses showed irregularities over defining multi-photon through single-photon quantum efficiency.
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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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Nikoghosyan AS, Martirosyan RM, Hakhoumian AA, Makaryan AH, Tadevosyan VR, Goltsman GN, et al. Effect of absorption on the efficiency of THz radiation generation in a nonlinear crystal placed into a waveguide. Armenian J Phys. 2018;11(4):257–62.
Abstract: The effect of THz radiation absorption on the efficiency of generation of coherent THz radiation in a nonlinear optical crystal placed into a metal rectangular waveguide is studied. The efficiency of the nonlinear conversion of optical laser radiation to the THz band is also a function of the phase-matching (PM) condition inside the nonlinear crystal. The method of partial filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. Phase matching was obtained by the proper choice of the thickness of the nonlinear crystal, namely the degree of partial filling of the waveguide. We have studied the THz radiation attenuation caused by the losses in both the metal walls of the waveguide and in the crystal, taking into account the dimension of the cross section of the waveguide, the degree of partial filling and its dielectric constant.
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Matyushkin YE, Gayduchenko IA, Moskotin MV, Goltsman GN, Fedorov GE, Rybin MG, et al. Graphene-layer and graphene-nanoribbon FETs as THz detectors. In: J. Phys.: Conf. Ser. Vol 1124.; 2018. 051054.
Abstract: We report on detection of sub-THz radiation (129-430 GHz) using graphene based asymmetric field-effect transistor (FET) structures with different channel geometry: monolayer graphene, graphene nanoribbons. In all devices types we observed the similar trends of response on sub-THz radiation. The response fell with increasing frequency at room temperature, but increased with increasing frequency at 77 K. Our calculations show that the change in the trend of the frequency dependence at 77 K is associated with the appearance of plasma waves in the graphene channel. Unusual properties of p-n junctions in graphene are highlighted using devices of special geometry.
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Moskotin MV, Gayduchenko IA, Goltsman GN, Titova N, Voronov BM, Fedorov GF, et al. Bolometric effect for detection of sub-THz radiation with devices based on carbon nanotubes. In: J. Phys.: Conf. Ser. Vol 1124.; 2018. 051050 (1 to 5).
Abstract: In this work we investigate the response on THz radiation of a FET device based on an individual carbon nanotube conductance channel. It was already shown, that the response of such devices can be either of diode rectification origin or of thermoelectric effect origin or of their combination. In this work we demonstrate that at 77K and 8K temperatures strong bolometric effect also makes a significant contribution to the response.
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