Enhancement of third harmonic generation induced by surface lattice resonances in plasmonic metasurfaces

TL;DR

This paper experimentally demonstrates that surface lattice resonances in plasmonic metasurfaces significantly enhance third harmonic generation, especially when multiple resonances are excited simultaneously, revealing new nonlinear optical phenomena.

Contribution

It introduces the experimental observation of enhanced THG via SLRs in plasmonic metasurfaces and explores effects of multiple resonances on nonlinear response.

Findings

SLRs are major contributors to THG enhancement.

Exciting multiple SLRs further boosts THG.

Maximum THG occurs with counter-propagating surface waves.

Abstract

We investigate experimentally Third Harmonic Generation (THG) from plasmonic metasurfaces consisting of two-dimensional rectangular lattices of centrosymmetric gold nano-bars. By varying the incidence angle and the lattice period, we show how Surface Lattice Resonances (SLRs) at the involved wavelengths are the major contributors in determining the magnitude of the nonlinear effects. A further boost on THG is observed when we excite together more than one SLR, either at the same or at different frequencies. When such multiple resonances take place, interesting phenomena are observed, such as maximum THG enhancement for counter-propagating surface waves along the metasurface, and cascading effect emulating a third-order nonlinearity.