APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelengths down to Hz Rates

ABSTRACT: For the SPECTRAP experiment at GSI, Germany, detectors with single-photon count-ing capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2×2 mm2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately-170◦C using liquid nitrogen. By operating the diodes close to the break-down voltage it is possible to achieve relative gains in excess of 2 · 104. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2 ·104. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230 s−1. With these settings the studied APDs are able to detect single-photons at 628 nm wavelength with a photo detection efficiency of (67 ± 7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13±3)%, again at a threshold of 6 mV