Observing the influence of second-harmonic tangential surface source in gold plasmonic nanostructures

TL;DR

This study uses scanning and simulation to analyze second harmonic generation in gold nanostructures, revealing the dominant role of tangential surface sources influenced by surface roughness, challenging previous assumptions.

Contribution

It demonstrates that tangential surface sources significantly contribute to SHG in gold nanostructures, a factor often overlooked in prior research.

Findings

Tangential surface sources dominate SHG in gold nanostructures.

Surface roughness affects the contribution of surface sources.

Normal surface sources have minimal impact on SHG.

Abstract

The origin of the second harmonic generation (SHG) from plasmonic structures remains a subject of debate. Here, we investigate SHG from gold plasmonic nanostructures by scanning nanostructures at the single-particle level to acquire two-dimensional (2D) SHG maps which are qualitatively and quantitatively compared with numerically simulated SHG maps. This approach allows us to discriminate the role played by the surface and bulk contributions to SHG. Our findings reveal that the tangential surface source contribution, often neglected in the literature, plays a dominant role and is affected by surface roughness. This is evident when comparing the SHG maps obtained from identically sized gold nanoparticles that are fabricated using physical and chemical techniques. Additionally, the normal surface source is not found to significantly impact SHG in these configurations.