Spatiotemporal optical vortex (STOV) polariton

Abstract: We confirm the existence of the spatiotemporal optical vortex (STOV) polariton and the value of its tOAM, verifying our theory of transverse orbital angular momentum in a simple dispersive medium [S. W. Hancock et al., Phys. Rev. Lett. 127, 193901 (2021)]. We also develop a physical picture of the polariton as a structure driven by torques induced by the ponderomotive force of the light in the presence of material dispersion. This is a new type of spatiotemporal torque unanticipated in our recent work [S. W. Hancock et al., Phys. Rev. X 14, 011031 (2024)]. These results are accomplished by high resolution particle-in-cell (PIC) simulations of STOV pulse reflection from and transmission through a fully ionized hydrogen plasma slab. The linear theory matches the PIC simulations up to near-critical plasma densities and near-relativistic field strengths. For higher intensities, optical tOAM becomes invested in collective modes of the plasma.