Abstract

A semiconductor laser with optical feedback is a simple and cheap system that displays a wealth of interesting nonlinear dynamics. Feedback can be utilized for linewidth narrowing, but unless precisely controlled, or carefully eliminated, it often degrades the laser properties, as exemplified by the coherence col lapsed state. In the talk, we will present experimental and theoretical results on the various instabilities found in semiconductor lasers at different levels of feedback. Starting at the lowest feedback levels, we discuss the occurence of mode jumping and show that it can be quantitatively explained by a simple analytical potential model. The model also explains the enhanced single mode behavior as the feedback level is increased. However, above a certain feedback level, relaxation oscillations become undamped, and a transition to chaos (coherence collapse) through quasiperiodicity interrupted by frequency locking is observed. In the transition region, we also observe competition between different attractors belonging to the same external cavity mode, and the existence of three-frequency quasiperiodic attractors is predicted theoretically. At still higher feedback levels and at low bias currents, low-frequency intensity fluctuations appear, which are shown to be explained in terms of bistability and dynamic formation of bistability.

© 1992 Optical Society of America