Linear gain anisotropy and mode profile asymmetry in spin-VCSELs: extended spin-flip models

Spin-VCSELs offer particularly rich polarization dynamics due to non-trivial interplay of spin-induced circular gain dichroism with microcavity-related linear anisotropies. One of their promising applications is a data transfer technology in which the information is carried by spin of electrons and photons, surpassing the standard intensity modulation technology in both speed and energy consumption. Over the years, modeling of spin-VCSELs has been basically monopolized by the so-called spin-flip model, which is however constructed assuming degenerate orthogonal modes. Moreover, any amplitude anisotropies are treated in a perturbative way using linear coupling terms. This can be misleading in case of gain anisotropies originating from QW strain or asymmetric light confinement. The situation is even more complicated in highly-birefringent devices such as grating-based spin-VCSELs, where the mode profile asymmetry leads to new coupling mechanisms of optical field components with opposite helicity. The aim of this work is to (i) explore the role of linear gain anisotropy in spin-VCSELs within the extended spin-flip model based on polarization-resolved coupled-mode theory and (ii) to further analyze the consequences of recently predicted coupling mechanisms appearing in highly-birefringent spin-VCSELs.