Resonant laser receiver for free-space laser communications

ABSTRACT Our approach to high receiver sensitivity is based on the optical field retaining its temporalform (and its coherence properties) despite attenuation on long-distance propagation. A field whose power corresponds to infrequent photon arrivals, if resonant with a high-finesseetalon, sees the full 100-percent transmittance, consistent with coherent field addition,although a photon detector would find the incident power to be very granular. If photon counting is deferred until the optical field is coherently amplified, the form of the field is kept intact. 1. INTRODUCTION The potential for covert operation and a virtual immunity to jamming threats makes lasercommunication systems very attractive for military space applications. Further, the potentially small size, weight, and prime power requirements and the high available bandwidth in the laser system are advantageous in other space applications where security and jam resistance are not necessary. Near-earth and deep-space data relay missions havebeen examined which could benefit greatly from laser data transfer.Previous BASG efforts have concentrated on laser communications beam-pointing subsystems,