Synchronization of semiconductor lasers with coexisting attractors

We study synchronization of unidirectionally coupled optical bistable systems. In particular, we consider two semiconductor lasers with an external cavity, which exhibit, when isolated, coexistence of two different attractors: fixed point and chaos, fixed point and one periodic orbit, and two periodic orbits with different periods. The analysis is performed with a cross-correlation function between the master and slave laser oscillations calculated with model equations based on the Lang-Kobayashi approach. Depending on both the laser operating point and the coupling strength, different bifurcations (Hopf, period doubling, saddle node, torus, and crisis) and diverse dynamical regimes (steady state, periodicity, quasiperiodicity, bistability, and chaos) occur in the route from asynchronous motion to complete synchronization. We show some similarities and differences between synchronization of monostable and bistable lasers.