Low-frequency fluctuations in vertical-cavity surface-emitting semiconductor lasers with optical feedback

We study the dynamics of a vertical-cavity surface-emitting laser operating near threshold and with isotropic optical feedback, using a model developed by San Miguel, Feng, and Moloney @Phys. Rev. A 52, 1728 ~1995!#. The model couples the polarization state of the electric field to the semiconductor medium by including the magnetic sublevels of the conduction and valence bands in the quantum wells. The laser dynamics depend significantly on the value of the relaxation rate, gs , of the material magnetization. For low relaxation rates the time-averaged intensity abruptly drops to zero and then recovers, a phenomenon revealed to be a sequence of picosecond pulses. The dropouts are similar to those occurring in conventional semiconductor lasers, but underlying the dropouts there is an antiphase competition between the time-averaged orthogonal linearly polarized components of the electric field. For large values of the relaxation rate, the dropouts tend to disappear and the time-averaged intensity is nearly constant. @S1050-2947~99!09603-1#