Arbitrary Total Angular Momentum Vectorial Holography Using Bi-Layer Metasurfaces.

Advanced holographic techniques are increasingly demanded for high-capacity and secure information processing. In this context, orbital angular momentum (OAM) stands out as a powerful resource for optical multiplexing, offering access to an unbounded set of orthogonal modes. To harness this potential, metasurfaces, with their considerable ability to control light, have emerged as key platforms for OAM-multiplexed holography. Nevertheless, conventional OAM holography suffers from limited polarization engineering capabilities due to the lack of chirality control in single-layer metasurfaces. Here, we introduce a bi-layer metasurface architecture that realizes total angular momentum (TAM) vectorial holography, where TAM represents the combination of spin angular momentum (SAM, equivalent to polarization) and OAM of light. In contrast to previous approaches, this scheme enables true polarization-OAM multiplexing, facilitating the independent generation of vectorial holographic images for each orthogonal TAM input state. This concept is validated numerically and experimentally, confirming the feasibility of TAM vectorial holography. The proposed scheme can be easily integrated with other recent holography generation approaches, such as vector beam multiplexing and bidirectional holography, thereby further expanding its multiplexing capability. This work establishes a versatile framework for advanced full-vectorial holography, showing how metasurfaces can unlock multiplexing strategies for emerging photonic systems.