Advances in Mid-Infrared Single-Photon Detection

The current state of the art of single-photon detectors operating in the mid-infrared wavelength range is reported in this review. These devices are essential for a wide range of applications, such as mid-infrared quantum communications, sensing, and metrology, which require detectors with high detection efficiency, low dark count rates, and low dead times. The technological challenge of moving from the well-performing and commercially available near-infrared single-photon detectors to mid-infrared detection is discussed. Different approaches are explored, spanning from the stoichiometric or geometric engineering of a large variety of materials for infrared applications to the exploitation of alternative novel materials and the implementation of proper detection schemes. The three most promising solutions are described in detail: superconductive nanowires, avalanche photodiodes, and photovoltaic detectors.