Nonlinear optical metasurfaces

A nonlinear optical metasurface, composed of spatially variant meta-atoms, is a type of ultrathin nonlinear optical device. By appropriate material selection and symmetry design, it is possible to realize multidimensional manipulation of the degrees of freedom of the nonlinear waves generated on the metasurfaces, including the polarization, phase, and amplitude. This paper reviews the mechanisms of the generation of harmonic waves, four-wave mixing and terahertz waves on nonlinear photonic metasurfaces, and discusses wavefront engineering, optical holography and optical encryption in the nonlinear optical regime.