Dye concentration effects on the formation and relaxation dynamics of organic microcavity polaritons

In this study, we fabricated microcavities with a polymer thin film dispersed with dyes at various molecule concentrations as the cavity layer. We measured the angle dependence of the transmission spectra and compared the formation conditions for strong coupling. We also performed time-resolved measurements of polariton emission. Through these measurements, we investigated the influence of dye molecule concentration on the splitting energy and relaxation dynamics. We confirmed that the vacuum Rabi splitting energy is not determined solely by this spectrum area but is also influenced by other material parameters. Furthermore, although fast emission from the lower polariton branch was observed in microcavities with high dye concentrations, we experimentally discovered that reducing the concentration alters the relationship between the polariton levels and the intrinsic energy levels of the molecules. These results demonstrate that dye concentration significantly affects not only polariton formation in organic microcavities but also the associated relaxation processes.