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EPJ Web of Conferences

Energy Relaxtation and Hot Spot Formation in Superconducting Single Photon Detectors SSPDS

Irina Florya, Yu. P. Korneeva, M.V. Sidorova, Alexander D. Golikov, Igor A. Gayduchenko, Georgy E. Fedorov, Alexander A. Korneev, Boris M. Voronov, Gregory N Gol'tsman

Published Jan 1, 2015• 0 citations
Publisher

Abstract

We have studied the mechanism of energy relaxation and resistive state formation after absorption of a single photon for different wavelengths and materials of single photon detectors. Our results are in good agreement with the hot spot model.
DOI
10.1051/epjconf/201510310004

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Recent results for a superconducting single-photon counter are presented. The detection mechanism of the photon counter is based on the combined action of the hot-spot formation after photon absorption and the subsequent current-assisted formation of a normal domain in a thin and narrow superconducting strip. Dark count rates caused by fluctuations of the superconducting order parameter as a function of the applied current are discussed as well as the dependence of the spectral sensitivity on detector dimensions and material parameters.
We report an experimental investigation of the hot-spot evolution in superconducting single-photon detectors made of disordered superconducting materials with different diffusivity and energy downconversion time values, i.e., 33-nm-thick NbN and 23-nm-thick NbC films. We have demonstrated that, in NbC film, only 405-nm photons produce sufficiently large hot spot to trigger a single-photon response. The dependence of detection efficiency on bias current for 405-nm photons in NbC is similar to that for 3400-nm photons in NbN. In NbC, large diffusivity and downconversion time result in 1-D critical current suppression profile compared with the usual 2-D profile in NbN.
We have experimentally studied the supercurrent-assisted formation of the resistive state in nano-structured disordered superconducting Nb(N) films after absorption of a single optical to near-infrared photon. The efficiency of the resistive state formation has a pronounced spectral cut-off; corresponding threshold photon energy decreases with the bias current. Analysis of the experimental data in the framework of the refined hot-spot model suggests that the quantum yield for near-infrared photons increases with the photon energy. Relaxation of the resistive state depends on the photon energy making the phenomena feasible for the development of energy resolving single-photon detectors.
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