Design of wideband terahertz vortex beam generation using geometric phase metasurfaces
This paper presents a single-layer transmission-type metasurface based on geometric phase,which ena-bles the generation of broadband Terahertz vortex waves through the design and arrangement of metasurface unit struc-tures.The metasurface unit consists of a top layer with dual C-shaped metal rings and a bottom dielectric layer.By uti-lizing the geometric phase principle and rotating the metal structures,the phase of cross-polarized transmitted light can be controlled while maintaining the same transmission coefficient over a wide frequency range.By encoding the unit structures with rotation,an encoded metasurface is formed capable of generating vortex beams with different topological charges in a wide frequency band.Simulation results demonstrate the generation of vortex beams with topological char-ges of l=±1 in the frequency range of 1.38-1.92 THz,with a maximum cross-polarization transmission efficiency of 23％.close to the theoretical limit of a single-layer structure.
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