Synchronization of indirect and direct three coupled lasers in a ring

Abstract

We investigated systems of three non-identical lasers coupled to each other in a ring topology. We introduced the coupling mechanism between the two lasers by direct and indirect coupling methods. In the weak coupling limit, a stable phase lock between lasers occurred at a critical coupling value. The analytic method revealed that the coupled lasers are described by a model which showed an amplitude and a phase dependence, for the first method of coupling. Also, the methodical investigations indicated that the coupled lasers in the second method of coupling are depicted by a coupled phase model only. Synchronization appeared in both methods at critical coupling constants. However, the synchronization mechanisms in the direct and indirect coupled lasers are interpreted in different ways. The unison behavior appeared at a small coupling constant for the indirect coupling technique in comparison to the case having the same conditions of the direct coupling technique.