Optical nonlinear metasurfaces formed by plasmonic nanoantennas

We discuss the possibility of significantly enhancing second-order optical nonlinearities with ultrathin planar arrays of plasmonic nanoantennas, forming nonlinear optical metasurfaces. We show that efficient wave mixing may be obtained at the nanoantenna loads, boosted by the plasmonic features and large field enhancement, which typically characterize optical nanoantenna designs. We then discuss two exciting applications of the proposed geometry: large frequency conversion efficiency and efficient phase-conjugation for sub-wavelength imaging.