Bifunctional metasurface for independently generating vortex beams and pencil beams

We propose a novel reflective metasurface composed of geometric phase elements to realize a bifunctional electromagnetic (EM) device. The proposed metasurface can realize distinct EM functions in response to different circularly polarized incidence. As a proof of concept, we have integrated two functions into one metasurface design, which aims to generate symmetrical twin vortex beams under the mumination of incidence with left circular polarization while twin pencil beams for right circular polarization. We have fabricated the metasurface and good agreements are observed between the measurement and simulation. This method could pave a new way to design bifunctional devices working for circular polarized wave.