Different regimes of low-frequency fluctuations in vertical-cavity surface-emitting lasers

摘要

We show that vertical-cavity surface-emitting lasers (VCSEL) subject to a polarization preserving optical feedback from a long external cavity may exhibit two different types of low-frequency fluctuations (LFF) regime. In both types, the total intensity shows random drops and then recovers gradually to its original value. But the two LFF types are clearly distinguished by the behavior of the x- and y-linearly polarized (LP) modes. Type I LFF is characterized by the fact that the x- and y-LP modes compete with nearly equal power, while type II LFF is characterized by intensity dropouts in the dominant polarization mode and intensity bursts in the depressed mode. We analyze the parameter regions in which these different LFF occur and characterize them further. Our numerical results suggest that a transition from one LFF type to the other may be experimentally observed by modifying the frequency difference and/or the gain-to-loss ratio of the two LP modes. The LFF we present is an example of vectorial chaos, which may be of use for multichannel secure communication systems using chaotic light.