A single-layer dielectric metasurface enabling wave incidence direction control

Multi-layer three-dimensional (3D) metamaterials have emerged as a platform to realize multifunctional chiral devices such as for asymmetric transmission. However, the alignment and fabrication methods of 3D chiral metamaterials are quite complex and time-consuming, which deteriorate the pragmatic use of such devices. Here, a unique type of direction-controlled single-layer metasurface hologram consisting of low loss hydrogenated amorphous silicon meta-atoms is proposed. The hologram behaves like a chiral metasurface and generates two unique holographic images in the forward and backward directions. The observed direction-sensitivity is explained by the spin-dependent multiplexing of two independent single-layer metasurfaces. Our proposed metasurface has obvious advantages over multi-layer chiral structures in terms of ease of fabrication, robustness, scalability, and cost-effectiveness. Finite-difference time-domain simulations proved the feasibility of direction-controlled all-dielectric holograms with high transmission efficiency in the visible domain. Due to the relatively easy manufacturing method utilized, and the novel functionality, this work can empower practical applications using direction-dependent integrated functional devices.