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Author Jukna, A.; Kitaygorsky, J.; Pan, D.; Cross, A.; Perlman, A.; Komissarov, I.; Sobolewski, R.; Okunev, O.; Smirnov, K.; Korneev, A.; Chulkova, G.; Milostnaya, I.; Voronov, B.; Gol'tsman, G.
Title (down) Dynamics of hotspot formation in nanostructured superconducting stripes excited with single photons Type Journal Article
Year 2008 Publication Acta Physica Polonica A Abbreviated Journal Acta Physica Polonica A
Volume 113 Issue 3 Pages 955-958
Keywords SSPD, SNSPD
Abstract Dynamics of a resistive hotspot formation by near-infrared-wavelength single photons in nanowire-type superconducting NbN stripes was investigated. Numerical simulations of ultrafast thermalization of photon-excited nonequilibrium quasiparticles, their multiplication and out-diffusion from a site of the photon absorption demonstrate that 1.55 μm wavelength photons create in an ultrathin, two-dimensional superconducting film a resistive hotspot with the diameter which depends on the photon energy, and the nanowire temperature and biasing conditions. Our hotspot model indicates that under the subcritical current bias of the 2D stripe, the electric field penetrates the superconductor at the hotspot boundary, leading to suppression of the stripe superconducting properties and accelerated development of a voltage transient across the stripe.
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Area Expedition Conference
Notes Approved no
Call Number Serial 1414
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Author Goltsman, G.; Korneev, A.; Minaeva, O.; Rubtsova, I.; Chulkova, G.; Milostnaya, I.; Smirnov, K.; Voronov, B.; Lipatov, A. P.; Pearlman, A. J.; Cross, A.; Slysz, W.; Verevkin, A. A.; Sobolewski, R.
Title (down) Advanced nanostructured optical NbN single-photon detector operated at 2.0 K Type Conference Article
Year 2005 Publication Proc. SPIE Abbreviated Journal Proc. SPIE
Volume 5732 Issue Pages 520-529
Keywords NbN SSPD, SNSPD
Abstract We present our studies on quantum efficiency (QE), dark counts, and noise equivalent power (NEP) of the latest generation of nanostructured NbN superconducting single-photon detectors (SSPDs) operated at 2.0 K. Our SSPDs are based on 4 nm-thick NbN films, patterned by electron beam lithography as highly-uniform 100÷120-nm-wide meander-shaped stripes, covering the total area of 10x10 μm2 with the meander filling factor of 0.7. Advances in the fabrication process and low-temperature operation lead to QE as high as  30-40% for visible-light photons (0.56 μm wavelength)-the saturation value, limited by optical absorption of the NbN film. For 1.55 μm photons, QE was  20% and decreased exponentially with the wavelength reaching  0.02% at the 5-μm wavelength. Being operated at 2.0-K temperature the SSPDs revealed an exponential decrease of the dark count rate, what along with the high QE, resulted in the NEP as low as 5x10-21 W/Hz-1/2, the lowest value ever reported for near-infrared optical detectors. The SSPD counting rate was measured to be above 1 GHz with the pulse-to-pulse jitter below 20 ps. Our nanostructured NbN SSPDs operated at 2.0 K significantly outperform their semiconducting counterparts and find practical applications ranging from noninvasive testing of CMOS VLSI integrated circuits to ultrafast quantum communications and quantum cryptography.
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Corporate Author Thesis
Publisher Spie Place of Publication Editor Razeghi, M.; Brown, G.J.
Language Summary Language Original Title
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Area Expedition Conference Quantum Sensing and Nanophotonic Devices II
Notes Approved no
Call Number Serial 1478
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