Photon number resolving superconducting nanowire single-photon detectors

Superconducting nanowire single-photon detectors (SNSPDs) are attractive for a variety of applications like integrated photonics, quantum key distribution and deep space communication. They have a high detection efficiency, single photon sensitivity, low dark count rate and very good time resolution but they lack intrinsic photon number resolution (PNR). By splitting of the SNSPD in several pixels using integrated shunts quasi-PNR can be achieved, thereby allowing amplitude multiplexing of detected number of photons. We developed technology and demonstrated quasi-PNR functionality of SNSPDs made of 4.9 nm thick and 80 nm wide NbN nanowires on sapphire, which were shunted by integrated palladium resistors with a resistance of 20 Ohms. Optical excitation of these detectors with an SWIR fs-laser clearly shows a power-depending photon statistic. Further details on the study of operation and optical response of quasi-PNR SNSPD will be presented and discussed.