Circular-Polarization-Dependent Beam Deflection via Brillouin Zone Folding in Resonant Phase Gradient Metasurfaces

Phase gradient metasurfaces enabled by guided-mode resonances offer a flexible route to realize multifunctional beam deflection with extreme spectral resolution. The high angular dispersion of guided-mode resonances allows us to mold the wavefront of light by tailoring the photonic band structures of resonant metasurfaces, which is yet elusive. Herein, we present the experimental demonstration of circular-polarization-dependent beam deflection via Brillouin zone folding in resonant phase gradient metasurfaces. The symmetry breaking in resonant metasurfaces via a periodic perturbation can form photonic superlattices in metasurfaces, leading to Brillouin zone folding in the photonic band structures. As such, the photonic band is replicated and translated along the momentum axis depending on the polarization of light. Consequently, circularly polarized light is coupled to the resonant metasurface in the normal direction and then experiences circular-polarization-dependent beam deflection through a cross-polarized band transition. Our work may open new avenues to optical wavefront manipulation via photonic band engineering.