Polarization-frequency multiplexing holograms employing Bi-layered patterned coding metasurfaces

Abstract

A surge in interest surrounding metasurfaces has been witnessed in recent years, driven by their capability to autonomously manipulate electromagnetic wavefront (EM) in three-dimensional space. While the initial focus in metasurface research has often been on manipulating electromagnetic waves using single polarization and frequency schemes, significant advancements have been made to overcome these limitations. Recent developments have introduced multifunctional metasurfaces that enable simultaneous control over multiple frequencies and polarizations, substantially enhancing their capacity for information processing and communication. Building on these advancements, our work introduces a novel three-channel full-space metasurface that leverages double-face copper-cladded patterns on a single-layer substrate, significantly increasing channel capacity through both frequency and polarization multiplexing. In order to achieve efficient control of the EM wavefront in multi-frequency and polarization scenarios, a super unit cell-based approach is utilized, wherein high-performance meta-atoms are combined to form super unit cells with minimal interferences. Specifically, different functionalities can be achieved in full space under different wave polarizations and frequencies. To validate the concept, a metasurface sample is fabricated and experimentally tested. The experimental results agree with both theoretical predictions and simulations, confirming the effectiveness of a three-channel metasurface holography. The metasurface achieves independent control of the incident EM wave's polarization and frequency, thus enhancing information storage capacity and encryption security.