| The metasurface,two-dimensional counterpart of metamaterials,is an emerging concept that has attracted tremendous interest in recent years.Compared with bulky metameterials,metasurfaces have a much smaller thickness and naturally present lower energy dissipation and are easier for miniaturization and integration.Most of the current designs of metasurfaces rely on the introduction of scatterers or unit cells with complicated structures/shapes so that we can get the desired wave scattering.In this paper,we present a design paradigm of two-dimensional metasurfaces composed of homogenous dielectric nanowires only,which can reliably work at the near-infrared and visiblelight frequencies.The design principle is based on the coherent interference between electric and magnetic dipolar modes of a single nanowire,in conjunction with the near-field coupling interactions between neighbouring nanowires in a periodic array.No complicated refractive index profiles or metallic components are needed here.By assembling different nanowires into a super cell structure and choosing an appropriate lattice constant,we present an actual physical implementation of the Huygens surface.An effective manipulation on the transmitted wave direction is achieved with a close-to-unity transmittance.A metasurface-based planar lens with short focal distance is unambiguously demonstrated,and potential applications in the related fields are expected. |
