Additively Manufactured Multi-Material Ultrathin Metasurfaces for Broadband Circular Polarization Decoupled Beams and Orbital Angular Momentum Generation.

Abstract

Controlling the wavefront and manipulating the polarization of the electromagnetic wave using an ultrathin flat device are highly desirable in many emerging fields. To shape the wavefront between two decoupled orthogonal circular polarization states, that is, the right-hand circular polarization (RCP) and the left-hand circular polarization (LCP), most state-of-the-art metasurfaces (MSs) combine the propagation phase and Pancharatnam-Berry phase into meta-atoms. This article proposes a different strategy to fully decouple the LCP and RCP and control their wavefronts independently. By taking advantage of the conductive and dielectric multi-material-integrated additive manufacturing technique, the proposed transmissive MS has an ultrathin thickness (0.11 free-space wavelength) and controls the LCP and RCP wavefronts independently under linearly polarized incidence illumination. The proposed meta-atom consists of a receiving antenna on the top, a transmitting antenna at the bottom with a strip-line connecting them. The strip-line introduces the same phase shifts for both RCP and LCP waves, while the transmitting antenna with in-plane rotation leads to the opposite phase shifts for RCP and LCP waves. Therefore, the phase delays from the strip-line and the angular rotation of the transmitting antenna provide two degrees of freedom, enabling independent beam shaping of LCP and RCP waves. Two MSs with different functionalities are printed for proof-of-concept, and the performances are experimentally verified.