Multifunctional reflection type anisotropic metasurfaces in the terahertz band

Based on the convolution and superposition theorem, we propose a reflective anisotropic metasurface to realize the functions of deflection and superposition of vortex beams, bifocal focusing, and focusing vortex beam. At frequency of 1.04THz, two deflection vortex beams with topological charges of ( l =-1 and l =+2) and ( l =+1 and l =-2) are generated under x - and y -polarized terahertz wave incidence, respectively. At focal plane, 1200µm from the top layer of the proposed metasurface, one can see that the bifocal focusing along y -axis and x -axis are produced under x - and y -polarized terahertz wave incidence, respectively. Similarly, focusing vortex beams with l =+1 and l =-2 are realized under x - and y -polarized terahertz wave incidence, respectively. The designed metasurface can flexibly manipulate terahertz wave under different polarization waves incidence and has potential application prospects in fields of terahertz communication.