Generation of Dual-Circularly Polarized Vortex Beams Based on Broadband Spin-Decoupled Metasurface

The broadband spin-decoupled metasurface is highly desirable for wireless communication applications, which possesses the independent control of dual-circularly polarized microwaves. In this work, a group of double arrow-shaped meta-atoms is designed for generating orbital angular momentum(OAM) vortex beams with arbitrary topological charges and dual-circularly polarized vortex waves. The proposed meta-atoms have a broad bandwidth ranging from 12.67 to 19.20 GHz (41%), which realize conversion efficiency higher than 0.8 and a reflection phase coverage of 360o. Based on the Pancharatnam-Berry(PB) phase theory and the spin decoupling concept, they can also realize spin-decoupled phase change in dual-circular polarization by simultaneously manipulating the geometrical parameters and rotation angle of the meta-atom. Then, the helical phase profile is analyzed as a blueprint for the design of the metasurface array, which generates different order vortex beams under left-handed and right-handed circularly polarized (LCP/RCP) wave excitations. The corresponding energy weight and far-field electric field distribution of dual-circularly polarized vortex waves are achieved by numerical computation to verify the high performance of the proposed metasurfaces. This paper demonstrates that the proposed meta-atoms can actualize wideband with separate control of the dual-circularly polarized vortex wave.