Large-area microwire MoSi single-photon detectors at 1550nm wavelength

We demonstrate saturated internal detection efficiency at 1550nm wavelengths for meander-shaped superconducting nanowire single-photon detectors made of 3nm thick MoSi films with widths of 1 and 3 mu m and active areas up to 400x400 mu m(2). Despite hairpin turns and a large number of squares (up to 10(4)) in the device, the dark count rate was measured to be similar to 10(3)cps at 99% of the switching current. This value is about two orders of magnitude lower than the results reported recently for short MoSi devices with shunt resistors. We also found that 5nm thick MoSi detectors with the same geometry were insensitive to single near-infrared photons, which may be associated with different levels of suppression of the superconducting order parameter. However, our results obtained on 3nm thick MoSi devices are in good agreement with predictions in the frame of a kinetic-equation approach.