Synchronization Dynamics of Mutually Injected Passively Mode-Locked Semiconductor Lasers

The operation of two 40-GHz semiconductor passively mode locked lasers that are coupled under mutual injection is investigated using a finite-time domain travelling wave numerical model. A detailed mapping of the pulse properties versus the operating parameters and the coupling conditions shows that the lasers can operate with a high degree of synchronization when the optical distance between the lasers is around integer multiples of their cavity length. The synchronized operation is maintained within a significant range around integer values of the normalized laser distance, and depends on the laser pulsewidth and linewidth enhancement factor as well as on the repetition rate mismatch.