Geiger-mode avalanche photodiodes for laser communications and laser radar

Arrays of photon-counting avalanche photodiodes (APDs) enable laser-communications and laser-radar receivers with unprecedented sensitivity at 1.06-mum wavelength. Near room temperature, the best detectors have: 50% photon detection efficiency, 30-kHz dark count rate, and a 1-mus reset time to avoid after-pulsing. Arrays with 64 elements were fabricated in the InGaAsP/InP materials system and were bump-bonded to a custom CMOS integrated circuit (IC) with a novel nonblocking architecture to continuously report both time-of-arrival for incoming photons as well as their spatial location on the array. Larger arrays with 1024 elements were mated to custom read-out ICs that report time and location data at lower duty cycles (typically 1-5%) and are appropriate for pulsed laser-radar systems