Asymptotic theory of a large fiber-laser array passive phase locking (original) (raw)

Coherent laser beam combining is a potentially attractive way to increase the combined beam brightness beyond the technological limits to single-mode fiber lasers. Passive phase locking (PPL) does not need external management and leads to strong simplification of the system. A specific feature of fiber amplifiers and lasers is that they possess optical path differences of the magnitude of many wavelengths. The involved problem in the PPL approach is to specify an ultimate limit to the phase-locked laser-array size. Earlier studies confirm the stabilizing role of gain saturation on beam-combining efficiency. The purpose of our study is to decipher the desired effect of nonlinearity on the combining efficiency in two architectures of a globally coupled fiber-laser array: (I) an array of amplifiers in ring resonator configuration with spatially filtered feedback; (II) an array of lasers also with external feedback. The external-cavity feedback in both systems results in global coupling...