Orbital‐Angular‐Momentum‐Encrypted Holography Based on Coding Information Metasurface

Abstract Metasurface holography has shown great potentials to reconstruct the full‐wave information of electromagnetic (EM) waves, bringing benefits of high spatial resolution and good precision of reconstructed images. To obtain higher security of the metasurface holography, orbital‐angular‐momentum (OAM) of EM waves is taken into consideration as new freedom of the metasurface holography. The use two coding information metasurfaces is proposed to achieve the OAM‐encrypted holography. One metasurface is used to generate different OAM beams with l = ±1 helical mode indices, which functions as the OAM feed; while the other is used to integrate different OAM helical‐phase wavefronts into the holograms of the transmitted images, forming the OAM‐encrypted holography. The predesigned images are accurately decoded only when the OAM‐encrypted metasurface is illuminated by the incident OAM beams with the inverse helical mode indices ( l = ∓1) under the incidence of defined polarization states. Experimental results agree well with the theoretical design and numerical simulations, verifying the feasibility and security of the OAM‐encrypted holography. The proposed method will be a good candidate to enhance the secure communication systems and imaging systems.