Regensburg 2016 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 19: Superconductivity: Poster Session
TT 19.55: Poster
Montag, 7. März 2016, 15:00–18:00, Poster D
Study of single-spiral superconducting nanowire single-photon detectors in magnetic fields — •Ilya Charaev1, Robert Lusche2, Alexei Semenov2, Konstantin Ilin1, and Michael Siegel1 — 1Institut für Mikro- und Nanoelektronische Systeme, KIT, Hertzstraße 16, 76187 Karlsruhe — 2Institut für Optische Sensorsysteme, DLR, Rutherfordstraße 2, 12489 Berlin
We present single-spiral superconducting nanowire single-photon detectors (SNSPD) with critical currents Ic and detection efficiencies which were improved by applying a magnetic field B. The structures were made from 100 nm wide and 5 nm thick superconducting NbN nanowires. We investigated circular spirals and rectangular spirals, both with a pitch of 150 nm and superconducting transition temperature about 12 K. We achieved a more than 10 percent increase of the critical current in magnetic fields for rectangular spirals. Contrary, circular spirals showed fully symmetrical Ic(B) dependencies, with the maximum of Ic at zero field.
The detection efficiency of spirals has been studied in a wide spectral range and in magnetic fields up to 500 mT. In circular spirals, the rates of light and dark counts were symmetric in magnetic fields at all achievable experimental conditions. In rectangular spirals, photon count rates were asymmetric with the minima at opposite direction of the field than the maximum of Ic. Dark count rates in these structures also demonstrated asymmetric behavior with respect to the magnetic field for the whole range of applied bias currents.