High-resistivity niobium nitride films for unity-efficiency SMSPDs at telecom wavelengths and beyond

The sensitive element of superconducting single-photon detectors made in the form of a microstrip promise to resolve significant limitations caused by their typical design. However, attention should be paid to the problem of deterioration of the detection efficiency of devices with an increase of the width of the superconducting strip from nano- to microscale. This article demonstrates a possibility of achieving highly saturated detection efficiency of superconducting microstrip single-photon detectors by using high-resistivity niobium nitride films. The approach opens the way for employing fundamentally improved experimental devices.