Photon counting using a large area avalanche photodiode cooled to 100 K

We have detected single 650 nm photons with quantum efficiencies greater than 60% using a large area silicon avalanche photodiode. We cool a 5 mm diam commercially available device to 100 K and operate in the gain-mode. For most applications—from the near-infrared to the ultraviolet—this device is the most sensitive photon counting detector that has ever been demonstrated. In typical photon counting applications, this detector should prove to be between two and one hundred times more sensitive than the best currently available devices.