We propose to design coding metasurfaces based on the Pancharatnam-Berry (PB) phase. The proposed PB coding metasurface could control circularly polarized components of incident waves, by encoding geometric phase into the orientation angle of coding particles to generate 1-bit and multibit phase responses. We perform digital convolution operations on scattering patterns of the PB coding metasurface to reach flexible controls of the circularly polarized waves, forming spin-controlled multiple beams with different polarizations in free space, such as pencil beams and vortex beams carrying orbital angular momentum. Both numerical and experimental results demonstrate the excellent performance of the PB coding metasurface, which opens a pathway to novel types of multibeam generations and provides an effective way to expand the beam coverage for wireless communication applications.
Keywords: Pancharatnam-Berry phase; anisotropy; circularly polarized waves; coding metasurface; multiple beams; vortex beam.