Ultrathin nonlinear metasurfaces with continuous phase control at the nanoscale

We describe a novel class of ultrathin plasmonic metasurfaces able to provide nonlinear conversion efficiencies many orders of magnitude larger than any other nonlinear flat setup previously reported. This large efficiency is achieved over subwavelength thickness, avoiding the use of cumbersome phase matching techniques. In addition, we show how such metasurfaces can be designed to provide full control over the local phase of the generated signals, opening exciting prospects for creating nonlinear reflect- and transmittarrays able to tailor the emerging wavefronts at will, with direct application in light bending, focusing, and communication systems.