Design of a vortex metalens with high focusing efficiency using propagation phase

Three vortex-focused beams are produced with linearly polarized light along the x or y axis at a wavelength of 1550 nm. First, a polarization-independent vortex metalens with a topological charge of three and focal length of 3000 nm is designed by selecting cylindrical-shaped elements. This design has a focusing efficiency of 83%. Second, vortex beams with different focal lengths and topological charges are achieved by combining various shapes of structures. Both designs have a focusing efficiency of greater than 92%. The designed metasurface is of great significance to optical communication and radar detection.