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

We study the effect of lateral carrier diffusion on the transient turn-on o f a semiconductor laser with optical feedback. The numerical simulations ar e 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. Fo r 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 inten sity drops to a nearly zero value in between the pulses; for fast carrier d iffusion, 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 effe ct of diffusion is qualitatively well modelled by a non-linear gain saturat ion coefficient different from zero in the space-independent Lang-Kobayashi model. Copyright (C) 2001 John Wiley & Sons, Ltd.