Coupled-mode description for the polarization state of a vertical-cavity semiconductor laser

For symmetry reasons, vertical-cavity semiconductor lasers might be expected to show polarization isotropy. Practical devices, however, operate in a well-defined polarization state, which indicates the presence of residual anisotropies. We have performed a systematic experimental study of these residual anisotropies by applying additional anisotropies in a controlled and continuous way. The results are compared with a coupled-mode model that describes the effect of linear anisotropies on the polarization eigenmodes. We conclude that the polarization state of a practical device is dominantly determined by these linear anisotropies; nonlinear anisotropies are found to play at most a minor role.