After two decades of rapid development, metasurfaces play an irreplaceable role in the manipulation of surface electromagnetic waves. In this thesis, we will demonstrate two projects in the designing of multifunctional metasurfaces. The first project involves a metasurface for position sensor applications. We experimentally demonstrate that a metasurface with two independent collimation frequencies in orthogonal directions can function as a position sensor. The brand new sensing mechanism leads to important advantages in contrast to the traditional working principles, thus providing a novel avenue for coordinate sensing. The second project is the probing of the topological physics of the metasurface. The topological characteristics of energy bands have attracted substantial inte...[ Read more ]

After two decades of rapid development, metasurfaces play an irreplaceable role in the manipulation of surface electromagnetic waves. In this thesis, we will demonstrate two projects in the designing of multifunctional metasurfaces. The first project involves a metasurface for position sensor applications. We experimentally demonstrate that a metasurface with two independent collimation frequencies in orthogonal directions can function as a position sensor. The brand new sensing mechanism leads to important advantages in contrast to the traditional working principles, thus providing a novel avenue for coordinate sensing. The second project is the probing of the topological physics of the metasurface. The topological characteristics of energy bands have attracted substantial interest in condensed matter systems as well as in classic wave systems. Among these energy bands, the type-II Dirac point is a nodal degeneracy with tilted conical dispersion, leading to a peculiar crossing in the constant energy plane. Such nodal points have recently been found in electronic materials. The analogous topological feature in photonic systems remains a theoretical curiosity, with experimental realization expected to be challenging. We experimentally realize the type-II Dirac point by employing a metasurface architecture, where the band degeneracy point is protected by the underlying mirr or symmetry of the metasurface. Gapless edge modes are found and measured at the boundary between the different domains of the symmetry-broken metasurface. The designed metasurfaces are simple and practical platforms for realizing electromagnetic type-II Dirac points. Furthermore, their planar structure is a distinct advantage that facilitates applications in two-dimensional topological photonics.