Ultrawideband 3-bit multifunctional metasurfaces by completely spin-decoupled meta-atom.

The achievement of distinct wavefront reconstruction for orthogonally polarized electromagnetic (EM) waves in a broadband frequency range is extremely important in modern wireless communications. However, the development of circularly polarized wavefront modulation devices is hindered by conjugate symmetric phase responses introduced by the rotation-induced geometric phase. Herein, a spin-decoupled meta-atom with a novel structure is designed to independently tailor left-hand and right-hand circularly polarized incident waves over a broadband range of 12-28 GHz with a fractional bandwidth of 80%. By incorporating diagonal curvature-induced and conventional geometric phases, spin-dependent phase modulation covering the entire 2π range can be obtained. As a proof of concept, three prototypes are designed and manufactured. In addition, a four-channel imaging method is proposed to enhance the information capacity of the meta-hologram. Furthermore, the applications of the proposed spin-decoupled method are also investigated in metalens and orbital angular momentum. Both the calculation and experimentation demonstrate the feasibility of the proposed spin-decoupled phase modulation strategy, which has potential applications in information metasurfaces, metalens, wireless communications, and other fields.