Efficient nonlinear metasurfaces by using multiresonant high-Q plasmonic arrays

We numerically investigate second-harmonic generation from multiresonant plasmonic metasurfaces by designing an array consisting of L-shaped aluminum nanoparticles that simultaneously supports two surface lattice resonances with relatively high quality factors (>100). Using an approach based on the nonlinear discrete-dipole approximation, we predict an over million-fold enhancement of the emitted second-harmonic intensity from a particle at the center of the metasurface compared to an individual particle and estimate that conversion efficiencies of around 10^-5 could be achievable from the surface. Our results are an important step towards making nonlinear metasurfaces practical for nonlinear applications, such as for frequency conversion.