Nonlinearities and Electrical Field Effects on Merocyanine Exciton-Polariton Cavities

Recently a significant attention has been given to organic exciton-polaritons due to their promise to alter chemical reactions and realization of Bose-Einstein condensates at higher temperatures. Organic exciton-polaritons are quasiparticles emerging from hybridization of localized Frenkel excitons and photon modes in Fabry-Perot cavities. In resonance, this light and matter state appears as Rabi-split modes called upper and lower polaritons. Described by the Tavis-Cummings model, the splitting of this two level system increases with the concentration of the active molecule, however, the high level of disorder in organic thin films has raised concerns on the aplicability of this model. Alongside the additional high number of degrees of freedom of single molecules, disorder results in broadened absorption peaks. Here, we address one category of disorder, transition dipole moment orientational disorder, through the use of merocyanine dyes known for their hypsochromic/electrochromic effects and high dipole moments. Owing to their non-centrosymmetric donor and acceptor structure, these dyes possess large second-order hyperpolarizability values. We apply capacitance electrical fields in Fabry-Perot microcavities and perform steady-state reflectivity as well as electroreflectance measurements to assess the degree to which polariton Rabi-splitting deviates from the zero-field behavior and the extent to which these quasiparticles inherit the nonlinear properties of molecular excitons.