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Smirnov, K., Vachtomin, Y., Divochiy, A., Antipov, A., & Goltsman, G. (2015). The limitation of noise equivalent power by background radiation for infrared superconducting single photon detectors coupled to standard single mode optical fibers. Rus. J. Radio Electron., (5).
Abstract: We investigated the minimum level of the dark count rates and noise equivalent power of superconducting single photon detectors coupled to standard single mode optical fibers. We found that background radiation limits the minimum level of the dark count rates. We also proposed the effective method for reducing background radiation out of the required spectral range of the detector. Measured noise equivalent power of detector reaches 8.9×10-19 W×Hz1/2 at a wavelength of 1.55 μm and quantum efficiency 35%.
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Smirnov, K., Vachtomin, Y., Divochiy, A., Antipov, A., & Goltsman, G. (2015). Dependence of dark count rates in superconducting single photon detectors on the filtering effect of standard single mode optical fibers. Appl. Phys. Express, 8(2), 022501 (1 to 4).
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Sobolewski, R., Zhang, J., Slysz, W., Pearlman, A., Verevkin, A., Lipatov, A., et al. (2003). Ultrafast superconducting single-photon optical detectors. In J. Spigulis, J. Teteris, M. Ozolinsh, & A. Lusis (Eds.), Proc. SPIE (Vol. 5123, pp. 1–11). SPIE.
Abstract: We present a new class of single-photon devices for counting of both visible and infrared photons. Our superconducting single-photon detectors (SSPDs) are characterized by the intrinsic quantum efficiency (QE) reaching up to 100%, above 10 GHz counting rate, and negligible dark counts. The detection mechanism is based on the photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconducting stripe. The devices are fabricated from 3.5-nm-thick NbN films and operate at 4.2 K, well below the NbN superconducting transition temperature. Various continuous and pulsed laser sources in the wavelength range from 0.4 μm up to >3 μm were implemented in our experiments, enabling us to determine the detector QE in the photon-counting mode, response time, and jitter. For our best 3.5-nm-thick, 10×10 μm2-area devices, QE was found to reach almost 100% for any wavelength shorter than about 800 nm. For longer-wavelength (infrared) radiation, QE decreased exponentially with the photon wavelength increase. Time-resolved measurements of our SSPDs showed that the system-limited detector response pulse width was below 150 ps. The system jitter was measured to be 35 ps. In terms of the counting rate, jitter, and dark counts, the NbN SSPDs significantly outperform their semiconductor counterparts. Already identifeid and implemented applications of our devices range from noninvasive testing of semiconductor VLSI circuits to free-space quantum communications and quantum cryptography.
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Sobolewski, R., Xu, Y., Zheng, X., Williams, C., Zhang, J., Verevkin, A., et al. (2002). Spectral sensitivity of the NbN single-photon superconducting detector. IEICE Trans. Electron., E85-C(3), 797–802.
Abstract: We report our studies on the spectral sensitivity of superconducting NbN thin-film single-photon detectors (SPD's) capable of GHz counting rates of visible and near-infrared photons. In particular, it has been shown that a NbN SPD is sensitive to 1.55-µm wavelength radiation and can be used for quantum communication. Our SPD's exhibit experimentally measured intrinsic quantum efficiencies from 20% at 800 nm up to 1% at 1.55-µm wavelength. The devices demonstrate picosecond response time (<100 ps, limited by our readout system) and negligibly low dark counts. Spectral dependencies of photon counting of continuous-wave, 0.4-µm to 3.5-µm radiation, and 0.63-µm, 1.33-µm, and 1.55-µm laser-pulsed radiations are presented for the single-stripe-type and meander-type devices.
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Svechnikov, S. I., Finkel, M. I., Maslennikov, S. N., Vachtomin, Y. B., Smirnov, K. V., Seleznev, V. A., et al. (2006). Superconducting hot electron bolometer mixer for middle IR range. In Proc. 16th Int. Crimean Microwave and Telecommunication Technology (Vol. 2, pp. 686–687).
Abstract: The developed directly lens coupled hot electron bolometer (HEB) mixer was based on 5 nm superconducting NbN deposited on GaAs substrate. The layout of the structure, including 30x20 mcm^2 active area coupled with a 50 Ohm coplanar line, was patterned by photolithography. The responsivity of the mixer was measured in a direct detection mode in the 25-64 THz frequency range. The noise performance of the mixer and the directivity of the receiver were investigated in a heterodyne mode. A 10.6 mum wavelength CW CO2 laser was utilized as a local oscillator.
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