Ultrafast Manipulation of Strong Coupling in Metal-Molecular Aggregate Hybrid Nanostructures

We demonstrate an ultrafast manipulation of the Rabi splitting energy Omega(R) in a metal molecular aggregate hybrid nanostructure. Femtosecond excitation drastically alters the optical properties of a model system formed by coating a gold nanoslit array with a thin J-aggregated dye layer. Controlled and reversible transient switching from strong ( Omega(R) similar or equal to 55 meV) to weak ( Omega(R) approximate to 0) coupling on a sub-ps time scale is directly evidenced by mapping the nonequilibrium dispersion relations of the coupled excitations. Such a strong, externally controllable coupling of excitons and surface plasmon polaritons is of considerable interest for ultrafast all-optical switching applications in nanoscale plasmonic circuits.