3D Printed Spin-Decoupled Transmissive Metasurfaces Based on Versatile Broadband Cross-Polarization Rotation Meta-Atom

This article proposes 3D printed broadband transmissive metasurfaces for spin-decoupled wavefront shaping based on a versatile broadband cross-polarization rotation meta-atom. A meta-atom combining broadband cross-linear polarization dynamic phase and Pancharatnam-Berry (P-B) phase is demonstrated to realize spin-decoupled beam shaping. The meta-atom is built in an antenna-circuit-antenna fashion. Stacked patch antennas are used here as both the receiving and transmitting antennas because they can achieve wide bandwidth and good impedance matching to free space. By carefully selecting the phase delay lines' path, the meta-atom converts the x-polarized or y-polarized linear incident wave to its cross-polarization with the co-polarized components suppressed. The function also leads to the spin conversion for the circularly polarized incident wave. Thus, P-B phase-shifting will be introduced when the meta-atom is rotated. In addition, the transmission line provides the same dynamic phase delay for both left- and right-hand circular polarization (LHCP and RHCP) incident waves. Then, combining the two different phase-shifting methods, i.e., the P-B phase and dynamic phase, the LHCP and RHCP wavefront can be fully decoupled. Two different metasurfaces achieving spin-decoupled anomalous refraction carrying orbital angular momentum (OAM) with different topological charges are simulated and experimentally verified for demonstration.