Multimode vertical-cavity surface-emitting lasers under spin-injection

Vertical-cavity surface-emitting lasers (VCSELs) dominate optical short-haul communication systems; however, recent studies have demonstrated that spin-VCSELs offer distinct advantages over their conventional counterparts for ultrafast optical communication. To date, research on spin-VCSELs has been restricted to the single-mode regime, while the inherently multimode nature of VCSEL operation has remained unexplored. In this work, we present an experimental investigation of multimode polarization dynamics in spin-VCSELs operating in multiple transverse modes. These measurements show polarization oscillations of the multimode regime, which have not been previously observed. Furthermore, we introduce an extended theoretical framework based on the classical spin-flip model, generalized to account for an arbitrary number of transverse modes. Using this model, we demonstrate that under specific conditions, the modulation bandwidth can be enhanced, thereby surpassing the single-mode performance limit.