# Using surface lattice resonances to engineer nonlinear optical processes in metal nanoparticle arrays

## TL;DR

This paper explores how surface lattice resonances in metal nanoparticle arrays can be engineered to significantly enhance various nonlinear optical processes, including harmonic generation and cascaded nonlinear interactions.

## Contribution

It introduces the use of surface lattice resonances to improve nonlinear optical interactions in nanoparticle arrays, focusing on sum-frequency, difference-frequency, and third-harmonic generation.

## Key findings

- SLRs can enhance nonlinear optical processes in metal nanoparticle arrays.
- Engineered arrays can boost third-harmonic generation efficiency.
- Cascaded nonlinear processes enable higher-order nonlinear interactions.

## Abstract

Collective responses of localized surface plasmon resonances, known as surface lattice resonances (SLRs) in metal nanoparticle arrays, can lead to high quality factors (~100), large local-field enhancements and strong light-matter interactions. SLRs have found many applications in linear optics, but little work of the influence of SLRs on nonlinear optics has been reported. Here we show how SLRs could be utilized to enhance nonlinear optical interactions. We devote special attention to the sum-frequency, difference-frequency, and third-harmonic generation processes because of their potential for the realization of novel sources of light. We also demonstrate how such arrays could be engineered to enhance higher-order nonlinear optical interactions through cascaded nonlinear processes. In particular, we demonstrate how the efficiency of third-harmonic generation could be engineered via cascaded second-order responses.