20 research outputs found
High-efficiency WSi superconducting nanowire single-photon detectors operating at 2.5 K
We investigate the operation of WSi superconducting nanowire single-photon
detectors (SNSPDs) at 2.5 K, a temperature which is ~ 70 % of the
superconducting transition temperature (TC) of 3.4 K. We demonstrate saturation
of the system detection efficiency at 78 +- 2 % with a jitter of 191 ps. We
find that the jitter at 2.5 K is limited by the noise of the readout, and can
be improved through the use of cryogenic amplifiers. Operation of SNSPDs with
high efficiency at temperatures very close to TC appears to be a unique
property of amorphous WSi
High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films
We demonstrate high-efficiency superconducting nanowire single-photon
detectors (SNSPDs) fabricated from MoSi thin-films. We measure a maximum system
detection efficiency (SDE) of 87 +- 0.5 % at 1542 nm at a temperature of 0.7 K,
with a jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization
dependence as low as 3.4 +- 0.7 % The SDE curves show saturation of the
internal efficiency similar to WSi-based SNSPDs at temperatures as high as 2.3
K. We show that at similar cryogenic temperatures, MoSi SNSPDs achieve
efficiencies comparable to WSi-based SNSPDs with nearly a factor of two
reduction in jitter
Quasiparticle recombination in hotspots in superconducting current-carrying nanowires
We describe a kinetic model of recombination of nonequilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The model is developed to interpret two-photon detection experiments in which a single photon does not possess sufficient energy for breaking superconductivity at a fixed low bias current. We show that quasiparticle self-recombination in relaxing hotspots dominates diffusion expansion effects and explains the observed strong bias current, wavelength, and temperature dependencies of hotspot relaxation in tungsten silicide superconducting nanowire single-photon detectors
Hotspot relaxation dynamics in a current-carrying superconductor
We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi superconducting nanowires as a function of bias current, bath temperature, and excitation wavelength. We observed that the hotspot relaxation time depends on bias current, temperature, and wavelength. We explained this effect with a model based on quasiparticle recombination, which provides insight into the quasiparticle dynamics of superconductors. © 2016 American Physical Society
A four-pixel single-photon pulse-position array fabricated from WSi superconducting nanowire single-photon detectors
Hotspot dynamics in current carrying WSi superconducting nanowires
We measured the temporal dynamics of optically excited hotspots in current-carrying WSi superconducting nanowires as a function of bias current, temperature and excitation wavelength, observing an unexpected effect: hotspot relaxation depends strongly on bias current