Revisiting the linear and nonlinear optical properties of nanoparticle-on-mirror–type plasmonic metasurfaces with transformation optics

We study the linear optical response and second-harmonic generation from a nanoparticle-on-mirror (NPoM) plasmonic metasurface composed of a nanoparticle array on top of a metal surface. By using transformation optics, the NPoM system is transformed into a simple geometry for the sake of an analytical solution, relaxing the analytical dilemma faced by the NPoM structure. In linear and nonlinear nanophotonics, our analytical method provides a unique understanding of the underlying physical process and endows an efficient scenario in the optical design for the widely used NPoM system.