Superconducting single photon detectors based on parallel NbN nanowires

Abstract

Ultrathin NbN nanowires is the material of choice for superconducting single photon detectors (SSPD) due to the good efficiency, dark count rate and timing jitter at 1550 nm wavelength obtained. These performance parameters are achieved using nanowires a few nanometers thick and 100 nm wide patterned into a meander shape in order to achieve area coverage. The meander shape effectively makes the SSPD of a single very long nanowire in turn giving it a significant inductance which limits the maximum count rate of the detector. Recently, we demonstrated how one can exploit a cascade switch to the normal state of nanowires connected in <i>parallel</i> to significantly reduce the SSPD inductance and increase the signal amplitude. Here we present how one can configure SSPDs that uses multiple cascade switches to the normal state. We show how this principle can be used to expand the SSPD coverage area with a very limited increase in detector inductance with area. Finally we discuss our first results obtained with SSPD based on the multiple cascade switch principle, showing correct operation, increased operational bias range and increased signal pulse amplitudes.