Multimode dynamics in laser diodes with optical feedback

The dynamical behavior of semiconductor lasers subject to external optical feedback is analyzed using an approach based on the theory of whole-universe laser modes [R. Lang, M.O. Scully, and W. Lamb, Phys. Rev. A 7, 1788 (1972)]. The system is modeled as a coupled cavity formed by the laser diode and an external reflector. The leakage of each optical mode out of the cavity is characterized by its mode lifetime. The variation of the cavity mode lifetimes is the dominant mechanism which determines the regime of operation. The method yields the expected range of phenomena observed when a laser diode is subjected to optical feedback, without a priori assumptions of the regime of behavior or of the resulting mode wavelengths. For strong optical feedback the imbalance of the lifetimes ensures that a single mode dominates. At other feedback levels the system exhibits chaotic dynamics or stable, multimode operation.