Simultaneously giant enhancement of Förster resonance energy transfer rate and efficiency based on plasmonic excitations

By using an exact multiscattering electromagnetic Green's function method, we present rigorous calculations on the rate and efficiency of Förster resonance energy transfer (FRET) from a donor to an acceptor when they are located in the hotspots of nanoparticle clusters. A nonlocal effect has been considered by using a hydrodynamic model. It is found that the FRET rate and efficiency can be enhanced simultaneously by more than 9 and 3 orders of magnitude, respectively, due to the strong coupling plasmon resonances originating from collective excitations of nanoparticle clusters. The physical origins for these phenomena have been disclosed. Two opposite phenomena, the energy transfer rate being independent or dependent on the local density of optical states (LDOS), have been observed in the same system under different conditions. These findings not only help us to understand the unresolved debate on how the FRET rate depends on the LDOS, but also provide a way to realize ultrafast the energy transfer process with ultrahigh efficiency.