Mutual coherence of laser solitons in coupled semiconductor resonators

Laser solitons are bistable localized laser beams that can be independently addressed by a local optical perturbation in form of a narrow beam. They can form in the transverse section of broad-area laser systems when suitable conditions are created. At difference with cavity solitons in driven microresonator, their phase is not fixed by any driving field and therefore no fixed phase relation between laser solitons should be expected. In this paper we analyze experimentally the mutual coherence of single-peak laser solitons and of multi-peaks laser solitons or clusters that coexist in the output beam of a laser system. We show that independent laser solitons are not mutually coherent while the peaks of a cluster have a well established mutual phase relationship.