High harmonic generation in solids driven by optical skyrmions

With their intricate vectorial structures in space, optical skyrmions have significantly expanded the landscape of topological optics and light–matter interactions. We theoretically investigate high harmonic generation in crystals driven by optical skyrmions. We find that although the skyrmion number is not conserved, the resulting high-order harmonics can exhibit a distinctive multi-vortex structure, whose features are shaped by both the topology of the optical skyrmions and the rotational symmetry of the crystal. The position of the vortex centers can be effectively tuned by employing different types of optical skyrmions. To elucidate the underlying physics, we develop a multi-absorption channel model based on the conservation laws of spin and orbital angular momentum. Our work explores the role of optical topology in extreme nonlinear light–matter interactions, offering new opportunities for the formation and manipulation of optical vortices and novel structured light fields in the visible and ultraviolet regimes.