Low noise InGaAs/InP single-photon detector for singlet oxygen detection

Single-photon detectors are the best option for applications where low noise measurements and/or high timing resolution are required. At wavelengths between 900 nm and 1700 nm, however, low noise detectors have typically been based on cryogenic superconducting technology, precluding their extended use in industrial or clinical applications. Here we present a practical (i.e. compact, reliable and affordable) detector, based on a negative feedback InGaAs/InP avalanche photodiode and exhibiting dark counts < 1 count-per-second at 10% efficiency, and with efficiencies of up to 27%. We show how this detector enables novel applications such as singlet-oxygen luminescence detection for Photo Dynamic Therapy (PDT) but can be an enabling technology also for a diverse set of applications in both quantum communication (e.g. long-distance quantum key distribution) and biomedical imaging.