Vortex Beam with Direction Control Based on Coding Chiral Metamirrors

With the growing channel demand in the interactive communication system, vortex beam with multi directions is of vital importance for high-efficiency communication. A chiral coding metamirror constructed with optically transparent material is proposed here to generate vortex beams carrying different topological charges in different directions. Dispersionless phase diagram covering 360 degrees is achieved based on the theory of Pancharatnam-Berry phase. The proposed metamirror unit has circular dichroism (CD) with near-perfect spin-selective absorption across a wideband and is insensitive to incident angle. Multi vortex beams can thus be selectively generated at the designated frequency, which avoid information interference. In addition, vortex beams with direction control are realized based on phase gradient mechanism.