Broadband Polarization Conversion Transmissive Janus Metasurface

This study addresses the limitations of conventional metasurfaces, which exhibit symmetric electromagnetic responses under forward and backward incidences and are difficult to achieve distinct functionalities and wavefront control. A multi-layer metasurface based on a polarization-ordered binary double-sided design is proposed. By breaking spatial symmetry at the structural level, diode-like asymmetric transmission and independent wavefront control are achieved. The design adopts a checkerboard-like staggered arrangement of unit cells, enabling different functionalities under forward and backward incidences for the same polarized wave. Orthogonal polarization conversion and broadband phase coverage are realized using multi-layer twisted metallic structures and a grating layer. Simulation results demonstrate that the metasurface achieves a - 30° beam deflection under forward incidence, while generating a vortex beam with topological charge 1 under backward incidence. The two channels exhibit good isolation, along with broadband and high transmission efficiency characteristics. This research provides new insights for high-performance non-reciprocal devices, bidirectional multi-functional integrated antennas, and information-encryption surfaces.