Multiple vibro-polaritons formation from a thin polyethylene film embedded in a resonant mid-infrared cavity

TL;DR

This study experimentally demonstrates multiple vibro-polariton modes in a polyethylene film strongly coupled with a mid-infrared cavity, providing insights into their dispersion and enabling precise modeling for future molecular film design.

Contribution

It presents the first detailed experimental resolution of multiple vibro-polariton modes in a thin polymer film within a resonant cavity, with accurate predictive modeling.

Findings

Measured Rabi frequencies of 111 cm$^{-1}$ and 29 cm$^{-1}$ for different vibrational modes.

Demonstrated precise prediction of polariton dispersion and Rabi splitting through numerical simulations.

Provided a method to accurately fit the dielectric function of molecular films.

Abstract

We experimentally resolve the dispersion of multiple vibro-polariton modes issued from the strong coupling of different vibrational bands of the methylene group (CH2) in a 2.56$\mu$m thick polyethylene film with the confined modes of a mid-infrared Fabry-Perot micro-cavity. We measure a Rabi frequency of 111 cm$^{-1}$ for the stretching doublet around 2950 cm$^{-1}$ and a Rabi frequency of 29 cm$^{-1}$ for the scissoring doublet around 1460 cm$^{-1}$. This simple experimental approach offers the possibility to accurately fit the measured molecular film dielectric function. We show that the polariton dispersion and Rabi splitting can be precisely predicted from numerical simulations, offering a valuable tool for the design of strongly coupled system and the development of novel molecular films with crystalline organization.