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Zhang, J., Słysz, W., Pearlman, A., Verevkin, A., Sobolewski, R., Okunev, O., et al. (2003). Time delay of resistive-state formation in superconducting stripes excited by single optical photons. Phys. Rev. B, 67(13), 132508 (1 to 4).
Abstract: We have observed a 65(±5)-ps time delay in the onset of a resistive-state formation in 10-nm-thick, 130-nm-wide NbN superconducting stripes exposed to single photons. The delay in the photoresponse decreased to zero when the stripe was irradiated by multi-photon (classical) optical pulses. Our NbN structures were kept at 4.2 K, well below the material’s critical temperature, and were illuminated by 100-fs-wide optical pulses. The time-delay phenomenon has been explained within the framework of a model based on photon-induced generation of a hotspot in the superconducting stripe and subsequent, supercurrent-assisted, resistive-state formation across the entire stripe cross section. The measured time delays in both the single-photon and two-photon detection regimes agree well with theoretical predictions of the resistive-state dynamics in one-dimensional superconducting stripes.
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Verevkin, A. A., Zhang, J., Slysz, W., Sobolewski, R., Lipatov, A. P., Okunev, O., et al. (2002). Superconducting single-photon detectors for GHz-rate free-space quantum communications. In J. C. Ricklin, & D. G. Voelz (Eds.), Proc. SPIE (Vol. 4821, pp. 447–454). SPIE.
Abstract: We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from 5% at wavelength λ = 1550 nm up to 10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm – 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography.
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Lipatov, A., Okunev, O., Smirnov, K., Chulkova, G., Korneev, A., Kouminov, P., et al. (2002). An ultrafast NbN hot-electron single-photon detector for electronic applications. Supercond. Sci. Technol., 15(12), 1689–1692.
Abstract: We present the latest generation of our superconducting single-photon detector (SPD), which can work from ultraviolet to mid-infrared optical radiation wavelengths. The detector combines a high speed of operation and low jitter with high quantum efficiency (QE) and very low dark count level. The technology enhancement allows us to produce ultrathin (3.5 nm thick) structures that demonstrate QE hundreds of times better, at 1.55 μm, than previous 10 nm thick SPDs. The best, 10 × 10 μm2, SPDs demonstrate QE up to 5% at 1.55 μm and up to 11% at 0.86 μm. The intrinsic detector QE, normalized to the film absorption coefficient, reaches 100% at bias currents above 0.9 Ic for photons with wavelengths shorter than 1.3 μm.
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Verevkin, A., Gershenzon, E. M., Gol'tsman, G. N., Ptitsina, N. G., Chulkova, G. M., Smirnov, K. S., et al. (2002). Direct measurements of energy relaxation times in two-dimensional structures under quasi-equilibrium conditions. In Mater. Sci. Forum (Vol. 384-3, pp. 107–116).
Abstract: A new microwave technique was successfully applied for direct studies of energy relaxation times in two-dimensional AlGaAs/GaAs structures under quasi-equilibrium conditions in the nanosecond and picosecond time scale. We report our results of energy relaxation time measurements in the temperature range 1.6-50 K, in quantum Hall effect regime in magnetic fields up to 4 T.
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Somani, S., Kasapi, S., Wilsher, K., Lo, W., Sobolewski, R., & Gol’tsman, G. (2001). New photon detector for device analysis: Superconducting single-photon detector based on a hot electron effect. J. Vac. Sci. Technol. B, 19(6), 2766–2769.
Abstract: A novel superconducting single-photon detector (SSPD), intrinsically capable of high quantum efficiency (up to 20%) over a wide spectral range (ultraviolet to infrared), with low dark counts (<1 cps), and fast (<40 ps) timing resolution, is described. This SSPD has been used to perform timing measurements on complementary metal–oxide–semiconductor integrated circuits (ICs) by detecting the infrared light emission from switching transistors. Measurements performed from the backside of a 0.13 μm geometry flip–chip IC are presented. Other potential applications for this detector are in telecommunications, quantum cryptography, biofluorescence, and chemical kinetics.
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