Honeycombed metasurface plate for generation of X-band orbital angular momentum beam

A honeycombed transmission metasurface based on hexagonal unit is proposed in this article for generation of orbital angular momentum (OAM) beam. The hexagonal metasurface unit is composed of five metal layers and is separated by four dielectric substrates. A metal layer with three etched crossed slots is placed in the middle of the substrates, and other four hexagonal metal layers with same dimensions are placed symmetrically on both sides. By simulating the unit comprehensively around the center frequency of 10 GHz, a list of units with good transmission coefficient and different phase shifts for metasurface design is obtained. Based on the hexagonal metasurface units, the configuration of the metasurface plate is presented and two models of +1 and +2 mode are designed accordingly. The simulated results show that the metasurface plate is insensitive to the incident wave polarization and is able to generate OAM beams from circularly polarized (CP) and linearly polarized (LP) incident plane waves. To validate the correctness of the simulation results, a +2 mode OAM metasurface plate is fabricated and measured, and a helical phase wavefront is obtained, which demonstrates the generation of OAM beam.