Generation of gamma photons carrying transverse orbital angular momentum driven by a spatiotemporal optical vortex laser

The generation of high-energy gamma photons carrying transverse orbital angular momentum (OAM) has been investigated by interacting an intense spatiotemporal optical vortex (STOV) laser with a solid target. The energy and transverse OAM of the STOV laser are first transferred to electrons, and these high-energy electrons subsequently transfer the energy and transverse OAM to gamma photons generated in QED regime. This process was analyzed and confirmed through two-dimensional Particle-in-Cell simulations. The simulation results demonstrate that under irradiation by a STOV laser with an intensity of 10²³ W/cm2, the OAM conversion efficiency from the laser to gamma photons reaches 4.75%. Most importantly, the spatial electric field profile of the STOV laser dictates the spatial energy density distribution of the emitted gamma photons. Specifically, when the driving STOV laser carries a topological charge l, the resulting gamma photons exhibit a spatiotemporal distribution characterized by |l| distinct nodal points.