Asymmetric multi-channel holography by cascaded plasmonic Janus metasurfaces

Janus metasurfaces have attracted considerable attention in encrypted communication, imaging, and display due to their unusual bidirectional asymmetric optical manipulation characteristics. Particularly, their multifunctionalization is of great significance for enhancing the compactness and integration of optical systems. However, the realization of multifunctional Janus metasurfaces in the optical band still faces enormous difficulties and challenges, which are essentially limited by the anti-error design and processing methods of multi-layer cascade metasurfaces. Here, a triple-layer Janus metasurface based on cascaded plasmonic nano-antenna arrays fully buried in SiO2 is constructed. Among them, the cascaded plasma nano-antenna consists of two types of enantiomers for each wavelength. Each enantiomer is fabricated with two layers of L-shaped nanostructures with phase modulation and one layer of dimer nanostructures with polarization selection stacked alternately along the optical axis. We experimentally show that the Janus metasurface achieves bidirectional asymmetric multi-channel holographic encryption, simultaneously using propagation direction, phase, polarization, and wavelength for the first time in the near-infrared band, which is expected to provide a frontier route for multifunctional optical displays, high-level optical information encryption, and large-capacity full-duplex communication.