Dynamics of vertical-cavity surface-emitting semiconductor lasers with polarization-isotropic optical feedback

We study the dynamics of a vertical-cavity surface-emitting laser with polarization isotropic optical feedback using the San Miguel, Feng, and Moloney model, which considers the role of carrier spin dynamics in both the conduction and the valence bands. Two transitions coupled to right- and left- circularly polarized light are coupled by spin-flip processes, which are characterized by the spin relaxation rate, (gamma) s. With moderately strong optical feedback and close to the solitary laser threshold the laser dynamics depend significantly on the value of (gamma) s. For low spin relaxation rates the time-averaged intensity often shows abrupt dropouts, similar to those observed in edge- emitting semiconductor lasers. Underlying the dropouts there is antiphase competition between the time-averaged orthogonal linearly polarized components of the electric field. For large values of the spin relaxation rate the dropouts tend to disappear and the time-averaged intensity is constant or nearly constant, depending on the stability of the linearly polarized states of the laser without feedback.