A three-dimensional, polarization-insensitive superconducting nanowire avalanche photodetector
Varun B. Verma, Francesco F. Marsili, Adriana E. Lita, Richard P. Mirin, Sae Woo Nam
Single-photon detectors are an essential tool for a wide range of applications in quantum information, quantum communications, and quantum optics. Over the past decade, superconducting nanowire single-photon detectors (SNSPDs) have become promising alternatives to conventional semiconductor avalanche photodiodes (APD) in the near-infrared region of the spectrum. In particular, SNSPDs based on niobium nitride (NbN) superconducting nanowires have demonstrated sub-50-ps timing jitter, fast reset times on the order of 10 ns, and low dark count rates below 1 kcps (counts per second), but generally suffer from low efficiencies of less than 20%. In addition, the efficiency of these detectors depends strongly on the polarization of the incident light. Recently, we reported promising results from SNSPDs based on an amorphous superconductor, tungsten silicide (WSi). Here we demonstrate a novel approach to improving the detection efficiency, removing the polarization dependence, and increasing the signal-to-noise ratio of conventional SNSPDs by vertically stacking two WSi SNSPDs and electrically connecting them in parallel, forming a three-dimensional superconducting nanowire avalanche photodetector (3D-SNAP). We expect this approach to have important applications for experiments in quantum optics requiring single-photon detection with high efficiency and polarization independence such as linear optical quantum computing and loophole-free Bell tests.