High performance terahertz vortex beam generator based on square-split-ring metasurfaces

Generating a vortex beam is a fundamental task due to the potential applications in wireless communication. Here we propose a kind of high-performance terahertz vortex beam generator with several topological numbers based on the square-split-ring metasurfaces. Via the Fabry-Perot resonance effect of the structure, the transmittance of an orthogonal polarization mode could be remarkably enhanced. We use a Laguerre-Gaussian (LG) mode for illustration and then simulate the far-field propagation of the LG beam by using phase superposition of focusing lens and vortex phase plates. The theoretical and simulation results agree well, which implies a bright application prospect.