Characteristics of polarization switching in vertical-cavity surface-emitting lasers

Polarization selection in small-area vertical-cavity surface-emitting lasers (VCSELs) is studied experimentally in dependence on injection current and substrate temperature in the vicinity of the minimum threshold condition. Different types of polarization switching (PS) are observed and analyzed: PS from the high to the low frequency mode, PS from low to high frequency and double switching (from high to low and back to high frequency). Whereas PS from the high to the low frequency mode is due to a change of sign of linear dichroism, the optical spectra show dynamical transition states for the other case which hint to the relevance of nonlinear effects. A comparison to the predictions of the SFM-model based on phase-amplitude coupling is given. The interplay of spatial and polarization effects can depend strongly on the ambient temperature.