Ultrahigh-sensitivity single-photon detection with linear-mode silicon avalanche photodiode

We developed an ultrahigh-sensitivity single-photon detector using a linear-mode avalanche photodiode (APD) with a cryogenic low-noise readout circuit; the APD is operated at 78 K. The noise-equivalent power of the detector is as low as 2.2 x 10(-20) W/Hz(1/2) at a wavelength of 450 nm. The photon-detection efficiency and dark-count rate (DCR) are 0.72 and 0.0008 counts/s, respectively. A low DCR is achieved by thermal treatment for reducing the trapped carriers when the thermal treatment temperature is above 100 K. (C) 2010 Optical Society of America