Asymmetric vortex generation in a time-switched magneto-optical Lorentz medium

By leveraging time interfaces and their combinations, time-switched metamaterials facilitate efficient wave manipulation in a uniform medium, circumventing energy conservation during propagation. Here, by merging time interfaces with magnetized Lorentz material dispersion, we demonstrate that a time-switched magneto-optical medium can enable the generation of vortex beams with topological charges of −2, 2 or 0, each steered by the spin state and incident direction of an initially vortex-free Bessel beam. Especially, by constructing dispersive photonic time crystals using the magneto-optical medium, we show that the efficiency of vortex generation and the asymmetry performance can be greatly improved through momentum bandgap engineering, surpassing the capabilities of a standalone temporal slab. Our approach broadens the functionalities of time-switched metamaterials, offering avenues for manipulating structured waves and paving the way for innovative solutions in wave engineering.