Formation of orbital angular momentum and focused beams based on chiral double-helical metamaterials

Abstract

We present a helical metamaterial that can generate orbital angular momentum and focused beams at about 77 GHz under the illumination of waveguide port. Helical metamaterials are 3-dimensional structures with strong couplings between the helical wires. Therefore, they are expected to be good candidates for generating phase shifts and controlling wave fronts with high efficiency. By adjusting the number of spiral circles, a full range of phases can be obtained. Arranging the helixes in an array with a constant phase gradient can generate focused beams, and beams with vortices.