Metasurface-generated holography has emerged as a promising route for fully reproducing vivid scenes by manipulating the optical properties of light using ultra-compact devices. However, achieving multiple holographic images using a single metasurface is still difficult due to the capacity limit of a single meta-atom. In this work, we present an inverse design method based on gradient-descent optimization to encode multiple pieces of holographic information into a single metasurface. The proposed method allows the inverse design of single-celled metasurfaces without the need for complex meta-atom design strategies, facilitating high-throughput fabrication using broadband low loss materials. By exploiting the proposed design method, both multiplane RGB color holograms and 3D holograms are designed and experimentally demonstrated. Up to eighteen distinct metasurface-generated holographic images are demonstrated, achieving the state-of-the-art data capacity of a single phase-only metasurface. To the best of our knowledge, we present the first experimental demonstration of metasurface-generated 3D holograms that have completely independent and distinct images in each plane. By demonstrating the high-density holographic information of a single metasurface, the current research findings provide a viable route for practical metasurfaces-generated holography, ultimately stepping towards applications in optical storage, displays, and full-color imaging.
