Enhanced Second Harmonic Generation from Coupled Asymmetric Plasmonic Metal Nanostructures

TL;DR

This paper demonstrates that Fano resonant coupling between asymmetric plasmonic metal nanostructures can significantly enhance second harmonic generation, with experimental validation showing up to 30-fold increase.

Contribution

It introduces a theoretical model and experimental evidence showing how asymmetric coupled nanostructures enhance second harmonic generation via Fano resonance.

Findings

Second harmonic generation is enhanced about 30 times with coupled nanostructures.

Fano resonant coupling is the key mechanism for enhancement.

Experimental results support the theoretical model.

Abstract

We show that second harmonic generation can be enhanced by Fano resonant coupling of asymmetric plasmonic metal nanostructures. We develop a theoretical model examining the effects of electromagnetic interaction between two metal nanostructures on the second harmonic generation. We compare the second harmonic generation efficiency of a single plasmonic metal nanostructure with that of two coupled ones. We show that second harmonic generation from a single metal nanostructure can be enhanced about 30 times by attaching a second metal nanostructure with a 10 times higher quality factor than that of the first one. The origin of this enhancement is Fano resonant coupling of the two metal nanostructures. We support our findings on Fano enhancement of second harmonic generation by an experimental study of a coupled plasmonic system composed of a silver nanoparticle and a silver nanowire on glass surface in which the ratio of the quality factors are also estimated to be around 10 times.