Coherent Detection with an Asynchronous Geiger Mode Array

Abstract

Large format arrays of coherent detectors enable several advanced EO sensing modes including aperture synthesis, turbulence compensation and velocity sensing. Coherent detector arrays that operate in a linear mode are desirable; however, they are often impractical because read-out'ss offering sufficient pixel density and A/D rates are not available. Photon-counting coherent detector arrays based on Geigermode Avalanche Photo-Diode (GmAPD) arrays are attractive because they offer large array format, and the output is digitized via the photon arrival times. Furthermore, asynchronous GmAPD arrays offer improved blocking efficiency which in turn improves the frequency fidelity. In fact, the response time of an asynchronous GmAPD macropixel exceeds the reset time of the individual detectors. In this paper we present the results of analysis, modeling and experiments that show the performance levels attainable with asynchronous GmAPD arrays.