Ultrastrongly Coupled Exciton–Polaritons in Metal-Clad Organic Semiconducto…

Ultrastrong exciton–photon coupling of Frenkel molecular excitons is demonstrated at room temperature in a metal-clad microcavity containing a thin fi lm of 2,7-bis[9,9-di(4-methylphenyl)-fl uoren-2-yl]-9,9-di(4-methylphenyl)fl uorene. A giant Rabi splitting of Ω ∼ 1 eV is measured using angle-resolved refl ectivity and bright photoluminescence is observed from the lower polariton branch.…