Second-harmonic generation from coupled plasmon modes in a single dimer of gold nanospheres

TL;DR

This paper demonstrates highly efficient second-harmonic generation from a gold nanosphere dimer, with the effect strongly dependent on nanoparticle contact proximity and coupled plasmon resonances, suggesting applications in high-resolution microscopy.

Contribution

It reveals that a gold nanosphere dimer exhibits enhanced second-harmonic generation when the particles are nearly touching, driven by coupled plasmon modes, a novel insight into nonlinear plasmonic effects.

Findings

Maximum SHG occurs at near-contact distances.

SHG intensity depends on excitation wavelength, indicating coupled plasmon resonance.

Potential application in high-resolution near-field microscopy.

Abstract

We show that a dimer made of two gold nanospheres exhibits a remarkable efficiency for second-harmonic generation under femtosecond optical excitation. The detectable nonlinear emission for the given particle size and excitation wavelength arises when the two nanoparticles are as close as possible to contact, as in situ controlled and measured using the tip of an atomic force microscope. The excitation wavelength dependence of the second-harmonic signal supports a coupled plasmon resonance origin with radiation from the dimer gap. This nanometer-size light source might be used for high-resolution near-field optical microscopy.