Optimized surface gratings for high-speed polarization switching in spin-VCSELs

Vertical-cavity surface-emitting lasers are limited to 30-50 GHz in conventional intensity modulation. Polarization modulation offers a promising alternative, exploiting birefringence-induced oscillations at much higher frequencies. We use rigorous coupled-wave analysis to design monolithic surface gratings that engineer birefringence for ultrafast modulation while minimizing loss anisotropy. By optimizing grating parameters and cap layer thickness, we achieve frequency splitting over 280 GHz with practical photon lifetimes and crucial near-zero dichroism. This work demonstrates a compact, fabrication-ready solution for birefringence control in spin-VCSELs, enabling their application in ultrafast polarization-based optical data transmission.