Turn-on transient dynamics of a semiconductor laser with optical feedback

We study the effect of lateral carrier diffusion on the transient turn-on of a semiconductor laser with optical feedback. The numerical simulations are based on the Lang-Kobayashi model, and on an extension of the model that includes lateral profiles for the carrier density and the optical field. For moderately strong feedback, intensity pulses characterize the dynamics of the turn-on, with a repetition rate at the external cavity round-trip time. We find that carrier diffusion has an important effect when the laser is biased close to the solitary threshold. For low carrier diffusion the intensity drops to a nearly zero value in between the pulses; for fast carrier diffusion, the spatial holes in the carrier profile burned by the intensity pulses are quickly replenished, and the intensity does not decay to a zero value in between the pulses. The results of our analysis show that the effect of diffusion is qualitatively well modelled by a non-linear gain saturation coefficient different from zero in the space-independent Lang-Kobayashi model. Copyright (C) 2001 John Wiley & Sons, Ltd.