Simultaneous/same-frequency/bidirectional terahertz vortex beam and beam-splitting generator

We proposed what we believe to be a novel simultaneous bidirectional terahertz vortex beam generator and beam splitter at the same frequency without changing external conditions. This metasurface consists of a five-layer structure, including a patterned monolayer of VO₂, a dielectric layer, a VO₂ thin film layer, a dielectric layer, and double-C metal pattern layer. The coding particles can achieve high reflection and transmission coefficients by rotating the dual-C metal pattern at different angles, while the phase meets the encoding requirements. The metasurface generates a transmitted and reflected vortex beam with topological charges of l = -1 and l = -2 at 0.9THz under left circularly polarized (LCP) wave incidence. Furthermore, through changing the arrangement of coding particles, the metasurface also produces the transmitted and reflected beam splitting with binary- and quaternary-beams at 0.9THz. It holds enormous potential in diverse applications such as terahertz wave stealth, beam generation, and wavelength division multiplexing techniques in the future.