Terahertz Dual-band Coding Metasurface for Vortex beam Manipulation

In this paper, a dual-band 3-bit coding metasurface for vortex beam manipulation is proposed. The unit cell of single-layer coding metasurface consists of two orthogonal split ring resonators (SSRs) for two operating frequencies. The dual-band two polarization reflected waves can be separately manipulated by the structure of SRRs. Based on Jones matrix theory, a dual-band 3-bit reflective metasurface is designed to generate two
$l=1$
vortex beams at 0.9 THz for the x-polarized incident wave, as well as, a vortex beam and four plane waves at 0.6 THz for the y-polarized incident wave.