Mid-infrared photon counting with superconducting nanowires

Superconducting Nanowire Single photon Detectors (SNSPDs) offer unparalleled performance for IR photon counting, combining close to unity quantum efficiency, low intrinsic noise and ultrafast timing jitter. The ability of SNSPDs to count photons in mid-IR band up to 7 um wavelength opens up new possibilities in quantum optics, laser ranging, free space Quantum Key Distribution (QKD) and astronomy. Here we report on development of mid-IR SNSPDs including device design, fabrication, optimisation of superconducting materials and characterisation. We present a characterisation setup covering 1.5 - 4.2 um spectral region based on tuneable optical parametric oscillator with picosecond long pulses. We then demonstrate the viability of mid infrared SNSPDs for a variety of applications and report the results from single photon light detection and ranging (LIDAR) experiment with 2.3 um photons. This work paves the way for future app in free space QKD, deep space communication and astronomy.