Ultranarrow-linewidth wavelength-vortex metasurface holography

Metasurface holograms harness multiple degrees of freedom of light to enhance information channel capacity. Traditionally, wavelength multiplexing holography with high-capacity information channel was only achievable through 3D volume holograms using Bragg diffraction. Here, we demonstrate ultranarrow-linewidth wavelength-vortex multiplexing holography in metasurface holograms. By applying elementary dispersion engineering, we develop a sparse k-vector-filtering aperture array in momentum space, enabling sharp wavelength selectivity combined with orbital angular momentum selectivity. Further leveraging transformer neural networks for the design of phase-only holograms, we showcase the reconstruction of up to 118 independent images from a single hologram, achieving a simulated ultranarrow linewidth of 2 nanometers within the visible range. We apply these developed metasurface holograms for holographic visual cryptography, attaining unprecedented security levels with an information rate over 2500 times higher than traditional methods. Our results open exciting avenues for the application of metasurface holograms in various fields, including 3D displays, holographic encryption, and optical artificial intelligence.