Plasmon coupled super- and sub- radiance from dye shells

Abstract

Coupled super- and sub- radiant emission of dye fluorescence near the plasmonic surface is shown to be an intrinsic property of the hybrid system. The bi-exponential decay is demonstrated for Au\\SiO2\\ATTO655 core-shell nanoparticles, which persists even when averaging over a broad range of the coupling parameter. The superradiant and subradiant states are distinct and exclusive by the identical permutational symmetry of the atom-field interaction Hamiltonian of the two-level system. Our analytical approach shows that starting from two emitters, coupled for example via the plasmon modes, the symmetry breaking occurs, making detectable the simultaneous existence of the fast super-radiance and the slow sub-radiance. The relaxation in the sub-radiant system occurs mainly due to the interaction with the plasmon modes. Our theory shows that the relaxation leads to the population of the sub-radiant states by dephasing the super-radiant Dicke states giving rise to the bi-exponential decay in agreement with the experiments. Even if we have a group of many coupled emitters or many groups of coupled emitters with different coupling parameters, the averaging will affect the emission among the super-radiant fast transitions and the sub-radiant slow transitions and keep these two group distinct.