Plasmonic metasurfaces

Plasmonic metasurfaces have opened a whole new paradigm for controlling electromagnetic waves in unprecedented ways, intriguing various novel optical effects and applications not achievable using natural materials or traditional optical devices. Gradient metasurfaces with a spatially varying phase response covering the entire 2p range are one of the most invigorating recent advances in nanophotonics and optics, providing a new platform to mold optical wavefronts into arbitrary shapes with subwavelength resolution. We first described the state-of-the-art plasmonic metasurfaces and separated them into four categories according to the technique utilized in phase modulation. Starting from the mechanisms using geometric effect such as multiresonance and gap-plasmonic metasurfaces, Pancharatnam-Berry phase metasurfaces, on the other hand, rely on the variation of orientation angles of scatterers with identical geometry. The recent progress in Huygen’s metasurfaces is especially promising for high-efficient transmitted applications. In addition to anomalous refraction and reflection demonstrated by these metasurfaces, an overview of their applications in polarization conversion as well as in wavefront shaping is discussed.