Stimulated Raman scattering of a spatiotemporal optical vortex beam

This study focuses on stimulated Raman scattering (SRS) of spatiotemporal optical vortex (STOV) beams to investigate the conservation and evolution of orbital angular momentum (OAM) during SRS in plasma. Two-dimensional particle-in-cell simulations revealed that transverse OAM is conserved by transferring from the pump light to the scattered light. However, the spatiotemporal diffraction of the pump light, which is usually inevitable for the STOV beam, causes the intensity of the scattered light to become inhomogeneous, which subsequently leads to the OAM of the scattered light being slightly different from that of the pump light. The spatiotemporal diffraction effect on the OAM becomes more pronounced for the pump light with a higher topological charge. This study demonstrates the transfer of OAM during STOV SRS and discusses the evolution of OAM over time in the process.