Modulation of Surface Plasmon due to the Inhomogeneity of a One-Dimensional Linear Array of Gold Nanoparticles Observed by Optical Second-Harmonic Generation Microscopy

Abstract

In this study, optical second-harmonic generation (SHG) microscopy of one-dimensional linear arrays of spherical Au nanoparticles (NPs) at the submicron scale was performed. Nine spherical Au NPs with a particle size of ∼100 nm were arrayed one-dimensionally in a groove on a glass substrate, and the array structure was observed by atomic force microscopy (AFM). The second-harmonic (SH) intensity distribution in the linear array was non-uniform and varied with photon energy. To understand the relationship between the SH signal and the local electric field related to the surface plasmon (SP) modes on the array, we calculated the local electric field generated between NPs based on the array structure of the particles observed by AFM. The SH intensity distribution and its wavelength dependence could be qualitatively explained by the local electric field distribution reflecting the spatially separated SP modes due to array inhomogeneity. SHG microscopy can be used to understand the details of SP interactions that reflect the microstructure of linear arrays, which are applied to nanoscale waveguides, filters, and antennas.