Centimeter-Scale Gold Nanoparticle Arrays for Spatial Mapping of the Second Harmonic and Two-Photon Luminescence

Fabricating highly homogeneous plasmonic nanostructures over a large area and optically evaluating their structural quality are challenging. Here, we propose an elegant approach to achieve various dense nanoparticle arrays with tunable symmetries over centimeter-scale dimensions and optically evaluate the structural quality by spatially mapping nonlinear emissions from L-, U-, and O-shaped individual nanoparticles. In particular, the spectral overlapping of the second harmonic (SH) and two-photon luminescence (TPL) emissions is separated, and excitation polarization dependence and spatial fluctuations of the nonlinear signal across the nanostructures are investigated. Narrow Gaussian-distributed peaks in the intensity histogram of SH and TPL emissions confirm the high-level uniformity of the fabricated arrays. Distinct spatial distributions of SH and TPL emissions are observed, and their spatial correlation is very weak over large-area nanostructures. Furthermore, SH signals are demonstrated as a more sensitive indicator of the structural quality of nanoparticle arrays. Our findings not only offer an efficient way of constructing versatile large-scale nanostructures but also enable spatial nonlinear optics tailoring for applications of nano-optics and quantum information.