Inverse design of broadband, strongly-coupled plexcitonic nonlinear metasurfaces

TL;DR

This paper introduces an inverse design strategy for hybrid plasmonic metasurfaces coupled with semiconductors, optimizing their nonlinear response through evolutionary algorithms, and demonstrates broadband, strongly-coupled nonlinear metasurfaces with enhanced signals.

Contribution

It presents a novel inverse design method for maximizing nonlinear responses in hybrid metasurfaces based on near-field enhancement optimization.

Findings

Strong coupling enhances nonlinear signals significantly.

Rabi splitting primarily determines the nonlinear response magnitude.

Hybrid structures enable broadband operation over hybridized modes.

Abstract

Hybrid photonic structures of plasmonic metasurfaces coupled to atomically thin semiconductors have emerged as a versatile platform for strong light-matter interaction, supporting both strong coupling and parametric nonlinearities. However, designing optimized nonlinear hybrid metasurfaces is a complex task, as the multiple parameters' contribution to the nonlinear response is elusive. Here we present a simple yet powerful strategy for maximizing the nonlinear response of the hybrid structures based on evolutionary inverse design of the metasurface's near-field enhancement around the excitonic frequency. We show that the strong coupling greatly enhances the nonlinear signal, and that its magnitude is mainly determined by the Rabi splitting, making it robust to geometrical variations of the metasurface. Furthermore, the large Rabi splitting attained by these hybrid structures enables broadband operation over the frequencies of the hybridized modes. Our results constitute a significant step towards achieving flexible nonlinear control, which can benefit applications in nonlinear frequency conversion, all-optical switching, and phase-controlled nonlinear metasurfaces.