Search for: All records

Abstract We present a microscopic model describing the transition to a strong coupling regime for an emitter resonantly coupled to a surface plasmon in a metal–dielectric structure. We demonstrate that the shape of scattering spectra is determined by an interplay of two distinct mechanisms. First is the near-field coupling between the emitter and the plasmon mode which underpins energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra prior to the transition to a strong coupling regime. The second mechanism is the Fano interference between the plasmon dipole and the plasmon-induced emitter’s dipole as the system interacts with the radiation field. We show that the Fano interference can strongly affect the overall shape of scattering spectra, leading to the inversion of spectral asymmetry that was recently reported in the experiment.

We present an analytical model describing the transition to a strong coupling regime for an ensemble of emitters resonantly coupled to a localized surface plasmon in a metal–dielectric structure. The response of a hybrid system to an external field is determined by two distinct mechanisms involving collective states of emitters interacting with the plasmon mode. The first mechanism is the near-field coupling between the bright collective state and the plasmon mode, which underpins the energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra in the weak coupling regime and to emergence of polaritonic bands as the system transitions to the strong coupling regime. The second mechanism is the Fano interference between the plasmon dipole moment and the plasmon-induced dipole moment of the bright collective state as the hybrid system interacts with the radiation field. The latter mechanism is greatly facilitated by plasmon-induced coherence in a system with the characteristic size below the diffraction limit as the individual emitters comprising the collective state are driven by the same alternating plasmon near field and, therefore, all oscillate in phase. This cooperative effect leads to scaling of the Fano asymmetry parameter and of the Fano functionmore »amplitude with the ensemble size, and therefore, it strongly affects the shape of scattering spectra for large ensembles. Specifically, with increasing emitter numbers, the Fano interference leads to a spectral weight shift toward the lower energy polaritonic band.

« less

We present a microscopic model describing the transition to strong coupling regime for an emitter resonantly coupled to a surface plasmon in a metal-dielectric structure. We demonstrate that the shape of scattering spectra is determined by an interplay of two distinct mechanisms. First is the near-field coupling between the emitter and the plasmon mode which underpins energy exchange between the system components and gives rise to exciton-induced transparency minimum in scattering spectra prior the transition to strong coupling regime. The second mechanism is Fano interference between the plasmon dipole and the plasmon-induced emitter's dipole as the system interacts with the radiation field. We show that the Fano interference can strongly affect the overall shape of scattering spectra, leading to the inversion of spectral asymmetry that was recently reported in the experiment.

We have studied emission kinetics of HITC laser dye on top of glass, smooth Au films, and randomly structured porous Au nanofoams. The observed concentration quenching of luminescence of highly concentrated dye on top of glass (energy transfer to acceptors) and the inhibition of the concentration quenching in vicinity of smooth Au films were in accord with our recent findings. Intriguingly, the emission kinetics recorded in different local spots of the Au nanofoam samples had a spread of the decay rates, which was large at low dye concentrations and became narrower with increase of the dye concentration. We infer that in different subvolumes of Au nanofoams, HITC molecules are coupled to the nanofoams weaker or stronger. The inhibition of the concentration quenching in Au nanofoams was stronger than on top of smooth Au films. This was true for all weakly and strongly coupled subvolumes contributing to the spread of the emission kinetics. The experimental observations were explained using theoretical model accounting for change in the Förster radius caused by the strong energy transfer to metal.