Physical insight into the polarization dynamics of semiconductor vertical-cavity lasers

The polarization properties of semiconductor vertical-cavity lasers (VCSELs) are generally described with a model introduced by San Miguel, Feng, and Moloney (SFM) in Phys. Rev. A 52, 1728 (1995). We have analyzed this SFM model from an experimentalist's point of view, using the idea that under certain conditions, which are satisfied by most practical VCSELs, the complicated spin dynamics can be adiabatically eliminated, leading to a managable analytical description. We hereby obtain new physical insight and intuitive pictures. One of the key results is the prediction that, via the spin dynamics, the presence of a strong lasing mode with a certain polarization will effectively lead to a broadening and frequency shift of the weak nonlasing mode with orthogonal polarization. This result gives a simple physical explanation for a polarization switch predicted by the model, and leads to further predictions that can be experimentally verified. The analysis also shows how the relaxation oscillations are related to the polarization dynamics and how they might be of crucial importance to experimentally determine the various parameters in the SFM model. We then discuss how the spin elimination reduces the SFM model to existing models for the polarization dynamics of class A (gas) lasers, with intuitive pictures of the polarization evolution on the Poincare sphere. Finally we will show how, within the context of adiabatic elimination, the cubic crystalline symmetry plays a special role in possible generalizations of the SFM model.