Single- and Multi-photon detection at telecom wavelengths using waveguide-integrated superconducting nanowires

Superconducting single photon detectors (SSPDs) offer broad optical bandwidth, low dark count rate, high detection efficiency and timing resolution [1]. Integrating those elements atop waveguide provide essential components for full scalable on-chip quantum photonic technology [2,3]. Here we demonstrate that niobium nitride (NbN) nanowire superconducting single photon detectors atop silicon nitride Si3N4 nanophotonic waveguide not only provide single photon capability but also can be used to discriminate large number of photons when operated under different biasing conditions. We present also a theoretical model that accurately fits our experimental results and allows us the extract the internal quantum efficiency of the waveguide integrated detectors.