Bidirectional quad-channel reflective CP-preserving metasurface with independent wavefront control capability

Dual-circular-polarization-preserving (CP-preserving) technology enables robust simultaneous dual-stream transmission by inherently maintaining polarization orthogonality, thereby maximizing link capacity and eliminating polarization mismatch. In this context, metasurfaces enable advanced electromagnetic (EM) wave control using a single aperture to achieve polarization-preserving capabilities. However, existing CP-preserving metasurfaces primarily manipulate EM waves in a single propagation direction, overlooking the potential for exploiting spatial resources and enhancing channel capacity in both propagation directions. This study proposes a bidirectional reflective CP-preserving metasurface that achieves broadband quad-channel CP preservation. The proposed meta-atom, featuring a multilayer architecture, physically realizes this capability by allocating distinct propagation pathways for incident CP waves from both spatial sides while introducing independent phase delays for each channel. On this basis, two demonstration prototypes for far-field beam steering and near-field holography in the Ku band are designed, fabricated, and measured, validating the excellent performance in both far-field and near-field regions. The advancement of the proposed metasurface enables it to serve as an ideal communication node for diverse application scenarios such as space-air-ground-sea integrated networks and indoor communication systems.