Polariton-mediated coupling of spatially separated quasi-degenerate porphyrin excitons.

When an ensemble of excitons strongly couples to single photons in a nano scale Fabry-Perot (FP) cavity, one drives the formation of hybrid light-matter states known as cavity polaritons. Previous studies have proposed polaritons formed from nearly degenerate Frenkel and Wannier-Mott excitons drives a photon-mediated entanglement of spatially separated material excitations across all light-matter coupling conditions. However, it remains unclear in what limit of near degeneracy these results exist and how to characterize similar entanglement for excitons stemming from highly disordered molecular ensembles. Previous studies show the Soret transition of porphyrin molecules enables the formation of robust molecular exciton cavity polaritons whose properties change relative to free space conditions. In this study, we form cavity polaritons using two quasi-degenerate porphyrin molecules, H₂TPP, and CuTPP, by strongly coupling them to cavity photons in a multilayer FP resonator structure. We show that despite their apparent degeneracy in linear absorption spectra, the fraction of the H₂TPP and CuTPP excitons in each polariton branch will vary as the cavity photon energy is tuned through its dispersion curve. The ability to tune the photonic and excitonic fraction of the polariton energy levels could be a pathway to create optical devices with selectively engineered optical properties.