Coherent beam combining: optical loss effects on power scaling

A model for a coherent array of amplifiers that has multiple stages and uses pairwise beam combining at the final stage has been developed. The model accounts for gain saturation of the individual amplifier elements, optical-coupling losses, and coherent-combining efficiency. The individual amplifier parameters are derived from experimental data. System size, efficiency, and output power are calculated as functions of optical-coupling efficiency and combining efficiency. Because of the exponential losses associated with pairwise beam combining, the coherent-combining losses are the dominant contribution to system efficiency reduction and increased system size.