High-Gain, Avalanche Photodiode Arrays for Deep Space Optical Communications

Space optical communications techniques are expected to be of great value when communicating at planetary distances. As opposed to RF systems, the high optical power concentration resulting from the small beam divergence will allow smaller diameter telescopes, less power and jam resistant communications. For deep space communications, the low optical level available for detection at the spacecraft presents challenging requirements in order to track the optical source position with extremely high accuracy. Current detection techniques do not have sufficient sensitivity at very low light levels encountered in these applications. This proposal presents a new high resolution, two-dimensional silicon avalanche photodiode focal plane array, with an internal gain higher than 108, fast time response and virtually without dead space between the sensing pixels. Phase I is designed to demonstrate the feasibility of producing high gain pixilated avalanche photodiodes by using integrated circuit planar technology. The detector is intended to be used as a acquisition/tracking detector at very low optical levels with applications in space optical communications.