Nonlinear Processes in Multi-Quantum-Well Plasmonic Metasurfaces:Electromagnetic Response, Saturation Effects, Limits and Potentials

TL;DR

This paper develops a comprehensive theoretical model for nonlinear plasmonic metasurfaces based on multi-quantum-wells, analyzing their electromagnetic response, saturation effects, and potential for efficient second-harmonic generation in the infrared.

Contribution

It introduces a homogeneous model that incorporates phase-matching, saturation, and losses, and provides analytical limits on nonlinear response, validated with experimental data.

Findings

Saturation limits constrain nonlinear efficiency.

Design guidelines for enhanced second-harmonic generation.

Validated model accurately predicts experimental results.

Abstract

Nonlinear metasurfaces based on coupling a locally enhanced plasmonic response to intersubband transitions of n-doped multi-quantum-wells (MQWs) have recently provided second-order susceptibilities orders of magnitude larger than any other nonlinear flat structure measured so far. Here, we present a comprehensive theory to characterize the electromagnetic response of nonlinear processes occurring in ultrathin MQW-based plasmonic metasurfaces, providing a homogeneous model that takes phase-matching at the unit-cell level and the influence of saturation and losses into account. In addition, the limits imposed by saturation of the MQW transitions on the nonlinear response of these metasurfaces are analytically derived, revealing useful guidelines to design devices with enhanced performance. Our approach is first validated using experimental data and then applied to theoretically investigate novel designs able to achieve significant second-harmonic generation efficiency in the infrared frequency band.