Ultrathin nonlinear metasurfaces

We present a novel class of ultrathin metasurfaces operating in a nonlinear regime, simultaneously providing generation efficiencies that are many orders of magnitude larger than in other nonlinear setups, and, at the same time, capable of controlling the local phase of the nonlinear signal with high precision and subwavelength resolution. The key to achieving such outstanding performance is combining a strong local field enhancement and polarization selectivity of plasmonic nano-antennas with extremely high nonlinearity of multi-quantum well semiconductor stacks. In this work, we discuss the operation principles of such metasurfaces and provide experimental and numerical results. We also show how a savvy application of Lorentz reciprocity principle allows for fast and efficient analysis and modeling of such metasurfaces consisting of thousands of elements.