Return-map for low-frequency fluctuations in semiconductor lasers with optical feedback

We show that the phenomenon of low-frequency fluctuations (LFF), commonly o bserved in semiconductor lasers with optical feedback, can be explained by a simple return-map, implying a tremendous simplification in the descriptio n of the slow time-scale dynamics of the system. Experimentally observed pa rameter dependencies are simply explained by the calculated return-maps. Ou r approach partly decouples the slow and the fast time-scale behaviour. The latter is often described in terms of chaotic itinerancy, but this does no t provide an explanation for the low-frequency fluctuations themselves. (C) 1999 Elsevier Science B.V. All rights reserved.