Abstract

Semiconductor lasers, by virtue of their unique physical properties and their extensive use in optical communication and data storage, are particularly appropriate vehicles for studying complex dynamic phenomena such as frequency locking, mode beating, instabilities, and chaos. Previous experiments using external cavity semiconductor lasers have demonstrated self-pulsations and chaos, especially when small tilt asymmetries are introduced into the feedback from the external reflector,¹ with subharmonic bifurcation and successive frequency locking being reported separately by different groups. Detailed experimental and theoretical studies of these systems have led us to develop a theoretical model which uses coherent rate equations modified for strong feedback systems. Using this model, we have predicted nearly sinusoidal self-pulsations and subharmonic bifurcations, in substantial agreement with our experiments. We have also observed period doubling and quasiperiodicity with increasing drive current in numerical simulations, depending on the values of various external parameters such as external mirror reflectivity and tilt angle. Here we compare theoretical and experimental data and discuss the physical mechanisms responsible for the observed phenomena. Particular attention will be paid to the significance of small tilt asymmetries, and the interaction between the resulting self-pulsations and various characteristic damping frequencies in determining the route to chaos.

© 1989 Optical Society of America