Ultranarrow-linewidth Wavelength-Vortex Metasurface Holography

TL;DR

This paper introduces a novel ultrathin metasurface hologram capable of multiplexing up to 118 images using ultranarrow linewidth wavelength-vortex encoding, significantly advancing high-capacity holography and secure cryptography.

Contribution

It develops a dispersion-engineered metasurface with sharp wavelength and vortex selectivity and employs neural networks for designing high-capacity multiplexing holograms.

Findings

Reconstructed 118 independent image channels from a single hologram

Achieved an ultranarrow linewidth of 2 nm in the visible range

Enhanced security in holographic cryptography with a 2500-fold information rate increase

Abstract

Ultrathin metasurface holograms, with thicknesses comparable to the operating wavelength, leverage multiple degrees of freedom of light to address independent image channels, thereby significantly enhancing information capacity. Although the wavelength of light can be used to encode holographic image channels, high-capacity wavelength-multiplexing holography has traditionally been achieved only through 3D volume holograms based on Bragg diffraction. We demonstrate ultranarrow-linewidth wavelength-vortex multiplexing holography in ultrathin metasurface holograms. By applying dispersion engineering to the elementary grating functions of a multiplexing hologram, we develop a sparse k-vector-filtering aperture array in momentum space that achieves sharp wavelength selectivity in conjunction with orbital angular momentum selectivity. Further leveraging transformer neural networks for the design of phase-only multiplexing holograms, we reconstruct up to 118 independent image channels from a single metasurface hologram, achieving an ultranarrow linewidth of 2 nm in the visible range. Finally, we apply the developed wavelength-vortex multiplexing metasurface holograms for holographic visual cryptography, achieving unprecedented security with an information rate more than 2500 times higher than that of traditional visual cryptography schemes. Our results open exciting avenues for the use of metasurface holograms in various applications, including 3D displays, holographic encryption, beam shaping, LiDAR, microscopy, data storage, and optical artificial intelligence.