Tunable optical spin Hall effect in an open cavity

The optical spin Hall effect (OSHE), resulting from photonic spin-orbit coupling, has become a pivotal phenomenon in nanophotonics. While a tunable optical spin Hall effect has been achieved in liquid-crystal-based anisotropic microcavities, a more general material-independent and broadband platform remains to be explored. In this work, we demonstrate dynamic manipulation on optical spin currents in an open cavity, where the strength and direction of the effective magnetic field experienced by photons can be precisely controlled. By exploring the cavity length dependence of the TE-TM mode splitting and photonic spin pattern both experimentally and theoretically, we unambiguously reveal the mechanism that governs the tunable OSHE. This approach relies on the intrinsic polarization properties of planar cavity modes, and is applicable for photonic spin control in any hybrid light-matter system within a broad optical bandwidth.