Enhancing vibrational light-matter coupling strength beyond the molecular concentration limit using plasmonic arrays

TL;DR

This paper demonstrates that integrating plasmonic nanorod arrays into vibrational cavities significantly enhances light-matter coupling strength beyond traditional molecular concentration limits, advancing vibropolaritonic chemistry and sensing applications.

Contribution

Introducing plasmonic nanorod arrays into vibrational cavities to surpass molecular concentration limits in coupling strength, with experimental and numerical validation.

Findings

Order of magnitude increase in coupling strength

Significant narrowing of plasmon linewidth

Potential applications in bio-sensing

Abstract

Vibrational strong coupling is emerging as a promising tool to modify molecular properties, by making use of hybrid light-matter states known as polaritons. Fabry-Perot cavities filled with organic molecules are typically used, and the molecular concentration limits the maximum reachable coupling strength. Developing methods to increase the coupling strength beyond the molecular concentration limit are highly desirable. In this letter, we investigate the effect of adding a gold nanorod array into a cavity containing pure organic molecules, using FT-IR microscopy and numerical modeling. Incorporation of the plasmonic nanorod array, that acts as artificial molecules, leads to an order of magnitude increase in the total coupling strength for the cavity filled with organic molecules. Additionally, we observe a significant narrowing of the plasmon linewidth inside the cavity. We anticipate that these results will be a step forward in exploring vibropolaritonic chemistry and may be used in plasmon based bio-sensors.