Photon counting at telecom wavelengths with commercial InGaAs/InP avalanche photodiodes: current performance

InGaAs/InP avalanche photodiodes operated in the so-called Geiger mode currently represent the best solution to detect single-photon beyond 900 nm. They cover the 1100-1650 nm wavelength interval, which includes in particular the two windows used for optical communications (1310 and 1550 nm). A detection efficiency at 1550 nm of 10% with a dark count probability of 10(-5) ns(-1) is common, although significant variations can be encountered. At this efficiency, a FWHM temporal response of 300 ps can be achieved. Afterpulses caused by charges trapped by defects in the high field region of the junction constitute the main performance impairment phenomenon. They enhance the dark count probability and reduce out-of-gate detector blindness. These photon counting detectors can be used in optical time-domain reflectometry to improve the spatial resolution and reduce dead-zone effects. Quantum key distribution over metropolitan area networks also constitutes an important application.