Polarization-state selection, polarization-state dynamics, and polarization switching of a quantum-well verticalcavity surface-emitting laser (VCSEL) for the lowest order transverse spatial mode of the laser is explored using a recently developed model that incorporates material birefringence, the saturable dispersion characteristic of semiconductor physics, and the sensitivity of the transitions in the material to the vector character of the electric field amplitude. Three features contribute to the observed linearly polarized states of emission: linear birefringence, linear gain or loss anisotropies, and an intermediate relaxation rate for imbalances in the populations of the magnetic sublevels. In the absence of either birefringence or saturable dispersion, the gain or loss anisotropies dictate stability for the linearly polarized mode with higher net gain; hence, switching is only possible if the relative strength of the net gain for the two modes is reversed. When birefringence and saturable dispersion are both present, there are possibilities of bistability, monostrability, and dynamical instability, including switching by destabilization of the mode with the higher gain to loss ratio in favor of the weaker mode. We compare our analytical and numerical results with recent experimental results on bistability and switchings caused by changes in the injection current and changes in the intensity of an injected optical signal.

Switching between linearly polarized states of slightly different optical frequencies with the same transversemode pattern is found, as the injection current is increased. Switchings found here for semiconductor rateequation models incorporating a vector electric field, birefringence, and the alpha factor are similar to previously reported experimental results.

We study polarization switching and transverse mode competition in Vertical Cavity Surface Emitting Lasers in the absence of temperature e ects. We use a model that incorporates the vector nature of the laser eld, saturable dispersion, di erent carrier populations associated with di erent magnetic sublevels of the conduction and heavy hole valence bands in quantum well media, spin-ip relaxation processes and cavity birefringence and dichroism. We consider both index-guided and gain-guided VCSELs, and we nd that spin-ip dynamics and linewidth enhancement factor are crucial for the selection of the polarization state corresponding to a given injection current. For index-guided VCSELs the e ect of spatial hole burning on the polarization behavior within the fundamental mode regime is discussed. For gain-guided VCSELs, transverse mode and polarization selection is studied within a Maxwell-Bloch approximation which includes eld di raction and carrier di usion. Polarization switching is found in the fundamental mode regime. The rst order transverse mode starts lasing orthogonally