Low-noise PPLN-based single-photon detector

This paper describes the detection of single photons, which have been transmitted through standard fiber at the telecom wavelength of 1310 nm. Following transmission, the 1310-nm photon is up-converted to 710 nm in a periodical-poled LiNbO3 (PPLN) waveguide and then detected by a silicon-based avalanche photodiode (Si-APD). The overall detection efficiency of the detector is 20%. We have also characterized the sensitivity of the PPLN’s efficiency to temperature and wavelength changes. We focused on the noise property of the up-conversion detector. Without classical channel copropagation, the dark count rate is 2.2 kHz, which is lower than current up-conversion detectors by more than one order of magnitude. The up-conversion detector is then applied to a QKD system, which is characterized and is shown to have a very strong performance.