Kovalyuk, V., Ferrari, S., Kahl, O., Semenov, A., Shcherbatenko, M., Lobanov, Y., et al. (2017). On-chip coherent detection with quantum limited sensitivity. Sci Rep, 7(1), 4812.
Abstract: While single photon detectors provide superior intensity sensitivity, spectral resolution is usually lost after the detection event. Yet for applications in low signal infrared spectroscopy recovering information about the photon's frequency contributions is essential. Here we use highly efficient waveguide integrated superconducting single-photon detectors for on-chip coherent detection. In a single nanophotonic device, we demonstrate both single-photon counting with up to 86% on-chip detection efficiency, as well as heterodyne coherent detection with spectral resolution f/f exceeding 10(11). By mixing a local oscillator with the single photon signal field, we observe frequency modulation at the intermediate frequency with ultra-low local oscillator power in the femto-Watt range. By optimizing the nanowire geometry and the working parameters of the detection scheme, we reach quantum-limited sensitivity. Our approach enables to realize matrix integrated heterodyne nanophotonic devices in the C-band wavelength range, for classical and quantum optics applications where single-photon counting as well as high spectral resolution are required simultaneously.
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Murphy, A., Semenov, A., Korneev, A., Korneeva, Y., Gol'tsman, G., & Bezryadin, A. (2015). Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts. Sci. Rep., 5, 10174 (1 to 10).
Abstract: We perform measurements of the switching current distributions of three w approximately 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijarvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.
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Gershenzon, E. M., Gershenzon, M. E., Gol'tsman, G. N., Semyonov, A. D., & Sergeev, A. V. (1984). Heating of electrons in superconductor in the resistive state due to electromagnetic radiation. Solid State Communications, 50(3), 207–212.
Abstract: The effect of heating electrons with respect to phonons in a thin superconducting film driven into the resistive state by the current and the external magnetic field has been observed and investigated. This effect caused by the electromagnetic radiation is manifested in the increased resistance of the film and is not selective over the frequency range from 1010 to 1015 Hz. That the effect is frequency independent under the conditions of strong electron scattering caused by static defects is explained by the decisive role of electron -electron collisions in forming the distribution function. The characteristic time of resistance change, obtained experimentally, corresponds to the relaxation time of the order parameter near the superconducting transition and to the relaxation time of the nonelastic electron-phonon interaction at lower temperatures and in lower magnetic fields.
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Bespalov, A. V., Gol'tsman, G. N., Semenov, A. D., & Renk, K. F. (1991). Determination of the far-infrared emission characteristic of a cyclotron p-germanium laser by use of a superconducting Nb detector. Solid State Communications, 80(7), 503–506.
Abstract: We studied the far-infrared emission characteristics of a cyclotron p-germanium laser using a broad-band superconducting Nb film detector. For magnetic fields between ∼25 kOe and ∼50 kOe, emission in a frequency range from ∼50 cm-1 to ∼100 cm-1 with maximum intensity around 90 cm-1 was obtained. We determined, for fixed magnetic fields, electric field dependences of the emission intensity taking into account that the total electric field is a sum of the applied and the Hall electric field. An analysis of the emission intensity characteristic gives evidence that transitions between the two lowest Landau levels of light holes are responsible for the laser action.
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Gershenzon, E. M., Gol'tsman, G. N., Semenov, A. D., & Sergeev, A. V. (1990). Mechanism of picosecond response of granular YBaCuO films to electromagnetic radiation. Solid State Communications, 76(4), 493–497.
Abstract: The ultrafast mechanisms of radiation detection in granular YBaCuO films are studied in the wide wavelength range from millimeter to near infrared. With the rise of radiation frequency the Josephson detection at the grain boundary weak links is replaced by electron heating into the grains. This change occurs in the submillimeter wavelength range. Electron-phonon relaxation time τeph is determined by direct measurements and analyses quasistationary electron heating. Temperature dependence of τeph at T ≤ 40 K was found to be τeph ∼ T−1. The results show that detectors with the response time of few picoseconds at nitrogen temperature are attainable.
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