Cooled single photon receiver for use in laser communication

Optical free-space communication is considered one of the most promising technologies for solving the future challenge of satellite communication.
However, due to the large distances from ground station to satellite, the signals received are very low. Avalanche photodiodes (APD) are one of the most sensitive components for detecting photons and can even detect single photons when operated in Geiger mode. However, this high sensitivity in this operating mode poses a number of challenges for the underlying circuit design.
In this project, an active circuit to cut off the APD and precise thermoelectric cooling to below -20°C was realised. This enables the implementation of a sensor for beam stabilisation of the received laser signal, which can work reliably even with few photons.