Metasurfaces with Planar Chiral Meta-Atoms for Spin Light Manipulation.

Spin light (i.e., circularly polarized light) manipulation based on metasurfaces with a controlled geometric phase (i.e., Pancharatnam-Berry (PB) phase) has achieved great successes according to its convenient design and robust performances, by which the phase control is mainly determined by the rotation angle of each meta-atom. This PB phase can be regarded as a global effect for spin light; here, we propose a local phase manipulation for metasurfaces with planar chiral meta-atoms. Planar chiral meta-atoms break fundamental symmetry restrictions and do not need a rotation for these kinds of meta-atoms to manipulate the spin light, which significantly expands the functionality of metasurface as it is incorporated with other modulations (e.g., PB phase, propagation phase). As an example, spin-decoupled holographic imaging is demonstrated with robust and broadband properties. Our work definitely enriches the design of metasurfaces and may trigger more exciting chiral-optics applications.