Passively mode-locked lasers subject to optical feedback: The role of amplitude-phase coupling

We investigate the impact of amplitude-phase coupling on the dynamics of a passively mode-locked laser subject to optical feedback. This is done using a delay differential equation model to calculate bifurcation diagrams in the plane of the feedback parameters. We find an increased complexity in the dynamics of the laser when the effective α-factors of the gain and absorber sections are different. With non-zero α-factors, quasiperiodic mode-locking can also be induced by resonant feedback and the extent of complex dynamical regions in the parameter plane increases.