Observation of strong exciton–photon coupling in an organic microcavity

An optical organic semiconductor microcavity showing the strong coupling regime was prepared. The dye 1,1′-diethyl-2,2′-cyanine (PIC) forming J-aggregates was used as optically active material in a planar λ/2-microcavity configuration. Stable thin layers of homogeneously distributed aggregates without any matrix were prepared by spin-coating of a specific salt of the dye [(PIC+)2B10H102−]. Strong exciton–photon coupling was demonstrated by the anticrossing of exciton and photon modes. A Rabi-splitting of more than 50 meV was observed in transmission measurements. The asymmetric normal mode splitting could be explained by the asymmetric absorption spectrum of the J-aggregate.