The SAPHIRA detector: a near-infrared photon counter for astronomy

The SAPHIRA is currently the only astronomical device capable of counting photons in the NIR while showing other performance easily comparable to the ubiquitous HAWAII arrays. Photon counting was previously only available in astronomy with high dark currents, prohibiting observation of many astronomical targets. Initiated by the European Southern Observatory for work on the VLT’s GRAVITY instrument, it was further developed by the University of Hawai’i and greatly improved, including a reduction of dark current by 3+ orders of magnitude. Development continues, with further improvements in dark current relative to avalanche gain and larger array sizes to be shown. Since initial deployments, it has now become a vital device in several astronomical instruments, and remains the only array capable of counting NIR photons for low-background astronomical targets.