Relaxation-oscillation-induced chaotic instabilities in modulated external-cavity semiconductor lasers

Abstract
We theoretically examine the consequences of modulating an external-cavity semiconductor laser around its mode-locking resonant frequency. When the modulation frequency is below resonance, the laser exhibits a three-frequency route to chaos. When the modulation frequency is above resonance, the laser oscillates in two- and three-frequency states. The chaotic instability is a result of the nonlinear interaction of three periodic modes of the laser system. These modes are dynamical manifestations of the composite cavity modelocking resonance, the applied field that is due to the modulation, and the laser relaxation oscillation.