High-efficiency generation of bi-functional holography with metasurfaces.

Holography is a highly desired technology in modern photonics, yet setups for traditional generating methods suffer from complexity and bulky sizes. While metasurface-based holography exhibits advantages of compactness and easy-fabrication, most meta-holograms realized so far exhibit only single functionality, with a few multifunctional ones suffering from imbalances of efficiency and device-thickness. Here, we propose a generic approach to design ultra-thin metasurfaces for realization of multiple holographic images with high efficiencies, and experimentally verify the concept in the telecom regime. We first design a series of high-efficiency reflective meta-atoms exhibiting incident-spin-delinked reflection phases governed by geometric and resonant mechanisms, and experimentally characterize their optical properties at wavelengths around 1,064 nm. We next experimentally demonstrate a single-functional meta-hologram as a benchmark test. Finally, we employ the designed meta-atoms to construct a metasurface with the thickness ∼1/4λ, and experimentally demonstrate its capability of generating two distinct holographic images under illuminations of circularly polarized light beams with different helicities, possessing generation efficiencies ∼48.08 %. Our work provides a highly-efficient and ultra-compact platform to generate multifunctional holographic images, which may inspire numerous applications in integration optics.