Polarization dynamics of two lasing modes at threshold in vertical-cavity surface-emitting lasers

This study presents theoretical and experimental investigations of the polarization dynamics of two lasing modes at threshold in vertical-cavity surface emitting lasers (VCSELs). The experimental results are compared to simulations within a model that is based on non-linear dynamics and relaxation processes among inversion populations with opposite spin. An important feature of this model is the frequency dependent susceptibility that is used to describe the gain medium. By use of this susceptibility, one is able to model effects that depend on the detuning between the cavity resonance and the band gap of the gain material. This detuning is changed in experiments by changing the temperature of the lasers. The obtained results hint to the fact that in the investigated devices spin relaxation processes have a strong impact on the polarization dynamics and selection at threshold.