Dramatic Enhancement of Third-Harmonic Generation in Plasmonic Nanostructures via Nonlocal Effects

TL;DR

This paper demonstrates that nonlocal effects in plasmonic nanostructures can significantly boost third-harmonic generation, surpassing traditional local-response limits by enabling deeper field penetration and much higher nonlinear responses.

Contribution

It reveals that nonlocal effects can enhance third-harmonic generation in nanostructures by four orders of magnitude, a novel insight into nonlinear plasmonics.

Findings

Nonlocal effects dramatically increase third-harmonic generation.

Field penetration inside metals is deeper due to nonlocality.

Nonlocality enhances effective nonlinearity by four orders of magnitude.

Abstract

Classical nonlocality in conducting nanostructures has been shown to dramatically alter the linear optical response, by placing a fundamental limit on the maximum field enhancement that can be achieved. This limit directly extends to all nonlinear processes, which depend on field amplitudes. A study of third-harmonic generation in metal film-coupled nanowires reveals that for sub-nanometer vacuum gaps the nonlocality enhances the effective nonlinearity by four orders of magnitude as the field penetrates deeper inside the metal than that predicted assuming a purely local electronic response.