Weak and Strong Coupling Properties of Surface Excitons

With high enough doping concentrations organic dye doped polymer materials exhibit negative real part of the permittivity within an energy range just above their material absorption, incurring surface exciton modes at these energies. Here, we report how such modes can be used to realize strong light-matter coupling with photoactive molecules. Our simulations reveal that surface excitons can facilitate strong coupling in terms of induced transparency, however, the polaritons may not be visible in the absorption since they can easily be located outside of the narrow negative permittivity regime. Moreover, we show that the surface exciton modes cannot couple strongly with the surface plasmons. Our findings shed light on the weak and strong coupling properties of surface excitons.