Broadband spin-decoupled metasurface with high-efficiency circular polarization conversion by encircling exceptional points

The exceptional topological (ET) phase, generated by encircling an exceptional point (EP) in a non-Hermitian metasurface, provides a novel approach for manipulating electromagnetic wavefronts. In this paper, a broadband spin-decoupled metasurface with high-efficiency circular polarization conversion is proposed. By rationally selecting the closed path encircling the EP in the parameter space composed of two split angles of the double split-ring resonator, the limitation that the ET phase can only effectively cover a full 2π range at a single frequency in traditional schemes is overcome. High-efficiency reflection with average amplitudes of circular-polarization conversion channels higher than 0.96 is achieved, while the ET phase maintains complete 2π coverage. Furthermore, Pancharatnam–Berry (PB) phases are introduced to realize independent manipulation of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) waves, successfully deflecting the two circularly polarized beams to preset angles. The application potential of the proposed metasurface in high-gain dual-circularly polarized beam manipulation is experimentally verified in the microwave band. This design method provides a new perspective for the design of high-performance, multi-scenario wavefront manipulation devices based on EPs.