Semiconductor spin-lasers with periodic gratings for ultrafast applications

Abstract

Vertical-Cavity Surface-Emitting Lasers (VCSELs) are key components in modern optical communication systems due to their compactness and energy efficiency. However, their conventional intensity modulation (IM) bandwidth is fundamentally limited by carrier and photon dynamics, typically to 30–50 GHz. Spin-polarized VCSELs (spin-VCSELs) offer an alternative through polarization modulation (PM), enabling much higher data rates by exploiting ultrafast polarization oscillations governed by birefringence. This thesis investigates monolithic integration of 1D surface gratings as a method to tailor birefringence in the laser cavity, while minimizing polarization damping caused by loss anisotropy. Simulations are performed using the PLaSK framework, a multiphysics solver based on Plane-Wave Admittance Method, which allows for self-consistent modeling of optical, thermal, and electrical phenomena in VCSELs. By optimizing grating parameters — period, fill factor, thickness—and cavity design, we demonstrate frequency splitting exceeding 280 GHz while preserving practical photon lifetimes. Furthermore, we show that modifying the cap layer can compensate for gain anisotropy, reducing dichroism to near-zero. The resulting design enables compact, fabrication-ready spin-VCSELs with integrated birefringence control, suitable for ultrafast polarization-encoded data transmission.