Strong exciton–plasmon couplings dependent on two localized modes in cuboid dielectric–metal core–shell resonators

In this paper, the strong exciton–plasmon couplings dependent on two localized modes are numerically and theoretically investigated in cuboid dielectric–metal core–shell resonators. For different resonance wavelengths, the electric fields of different modes can be highly localized in the dielectric gap layer, bringing about very small mode volumes. Through the active control of core–shell cavity parameters, the Rabi splitting and the anti-crossing dispersion are observed in the extinction spectrum, confirming the realization of strong coupling Both the multimode interference coupled mode theory and the Bloch equation are applied to explain the strong coupling in this system. After replacing the shell metal from silver to gold, the large red shift of resonance peaks exactly makes the high order mode strongly coupled with the same J-aggregate molecules, thus inducing slight spatial changes and reducing the required minimum number of the coupled excitons.