Anomalous scenario of the dynamic chaos onset in multimode laser diodes

Abstract

Anomalous transition to the regime of dynamic chaos in a multimode quantum-well heterolaser (λ = 635 nm) is possible as a result of an injection-current-induced change in the gain. A stable multimode regime (featuring more than ten longitudinal modes) is established near the lasing threshold under conditions of weak nonlinear coupling. As the injection current increases, the competition of modes results in a partial suppression of weak laser modes. At a certain excess of the gain over losses, a regime with hard excitation of four modes is realized that is characterized by the onset of a dynamic chaos manifested by irregular amplitude pulsation of modes, broadening of the optical spectrum, and loss of coherence. The loss of coherence is revealed by a decrease in the visibility of interference bands and by their chaotic shifts. An increase in the overall nonlinear coupling and the corresponding competition of modes leads to a decrease in the dimension of the self-oscillatory system and to the onset of a stable single-mode lasing regime.