Combining efficiency degraded by gain in passively phase-locked laser arrays: contribution of the spectral filtering.

Passive phase-locking of laser arrays is usually less efficient when the operating point is far above the laser threshold. We investigated the contribution due to the spectral filtering effect induced by the coupled cavities. Experiments carried out on a basic dual-arm laser as well as modeling show that some laser combining losses arise from the spectral filtering whose transmission windows have a non-uniform profile. A simple analytical model of the laser confirms this interpretation.

Active coherent combining of laser beam arrays by means of phase-intensity mapping in an optimization loop.

A new approach is proposed for the adaptive phase-locking of a set of parallel laser beams. It is based on an optical conversion of phase differences in the array into an intensity pattern which feeds an optimization algorithm for iterated adjustments of the phase modulators. A numerical analysis and proof of principle experiment support the method and demonstrate its speed.