We propose an ultra-thin planar metasurface with phase discontinuities for highly efficient beam steering. The effect benefits from the broadband transparency and flexible phase modulation of stacked metal/dielectric multi-layers that is perforated with coaxial annular apertures. Proof-of-principle experiments verify that an efficiency of 65% and a deflection angle of 18° at 10 GHz are achieved for the transmitted beam, which are also in good agreement with the finite-difference-method-in-time-domain (FDTD) simulations. The scheme shall be general for the design of beam-steering transmitters in all frequencies.

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We propose a scheme of metal/graphene plasmonic gratings for negative reflection. The existence of graphene ribbons, introducing abrupt discontinuity on tangential components of magnetic fields for scattering waves across a graphene interface, substantially alters the dispersion of surface states on plasmonic gratings such that negative reflection that is robust against the incidence angle and can be tuned in a wide frequency range as a function of Fermi energy of graphene. Circularly polarized incidence waves are reflected and split along specular and negative directions, with respective to transverse magnetic and electric polarization. Our findings are potentially helpful for light steering in integrated optical circuits.