Disordered ensembles of strongly coupled single-molecule plasmonic picocavities as nonlinear optical metamaterials

TL;DR

This paper explores how disordered ensembles of strongly coupled single-molecule plasmonic picocavities can serve as nonlinear optical metamaterials, demonstrating feasible room-temperature cross-phase modulation through strong light-matter interactions.

Contribution

It introduces a theoretical framework for using molecular picocavity ensembles as nonlinear optical devices, highlighting the role of strong coupling and disorder in enabling optical control.

Findings

Strong coupling induces significant refractive index changes.

Cross-phase modulation is achievable at room temperature with weak fields.

Disorder models show robustness of the nonlinear effects.

Abstract

We propose to use molecular picocavity ensembles as macroscopic coherent nonlinear optical devices enabled by nanoscale strong coupling. For a generic picocavity model that includes molecular and photonic disorder, we derive theoretical performance bounds for coherent cross-phase modulation signals using weak classical fields of different frequencies. We show that strong coupling of the picocavity {\it vacua} with a specific vibronic sideband in the molecular emission spectrum results in a significant variation of the effective refractive index of the metamaterial relative to a molecule-free scenario, due to a vacuum-induced Autler-Townes effect. For a realistic molecular disorder model, we demonstrate that cross-phase modulation of optical fields as weak as 10 kW/cm$^2$ is feasible using dilute ensembles of molecular picocavities at room temperature, provided that the confined vacuum is not resonantly driven by the external probe field}. Our work paves the way for the development of plasmonic metamaterials that exploit strong coupling for optical state preparation and quantum control.