Origin of optical second-harmonic generation in spherical gold nanoparticles: Local surface and nonlocal bulk contributions

TL;DR

This study investigates the origins of second-harmonic generation in spherical gold nanoparticles, distinguishing local surface and nonlocal bulk contributions through experimental and theoretical analysis involving plasmon interference and FEM simulations.

Contribution

It introduces a method to differentiate surface and bulk nonlinear contributions in gold nanoparticles using interference effects and FEM fitting, evaluating theoretical models.

Findings

Interference effects serve as fingerprints for nonlinear contributions.

FEM simulations effectively fit experimental SHG data.

Hydrodynamic and local density approximation models are critically assessed.

Abstract

The second-harmonic generation of 150 nm spherical gold nanoparticles is investigated both experimentally and theoretically. We demonstrate that the interference effects between dipolar and octupolar plasmons can be used as a fingerprint to discriminate the local surface and non-local bulk contributions to the second-harmonic generation. By fitting the experimental data with the electric fields computed with finite-element method (FEM) simulations, the Rudnick and Stern parameters weighting the relative nonlinear sources efficiencies are evaluated and the validity of the hydrodynamic model and the local density approximation approaches are discussed.