Diverse spatiotemporal high harmonic generation

This is the authors' abstract. We don't add key points for this paper.

A spatiotemporal optical vortex (STOV) has a transverse orbital angular momentum (TOAM) perpendicular to its direction of propagation. We propose the generation of intense spatiotemporal vortical high harmonics with tunable TOAM using two strong STOV beams that simultaneously interact with a solid thin foil from both sides. Theoretical predictions of harmonic order and topological charge were validated using particle-in-cell simulations. The results show that harmonics originate from the reflection and transmission of the two driving beams and that the ‘monochromaticity’ of the harmonics in the topological charge domain depends on the topological charges of the two driving beams.