Long-Range Dipole-Dipole Interactions in a Plasmonic Lattice.

Spontaneous emission of quantum emitters can be enhanced by increasing the local density of optical states, whereas engineering dipole-dipole interactions requires modifying the two-point spectral density function. Here, we experimentally demonstrate long-range dipole-dipole interactions (DDIs) mediated by surface lattice resonances in a plasmonic nanoparticle lattice. Using angle-resolved spectral measurements and fluorescence lifetime studies, we show that unique nanophotonic modes mediate long-range DDI between donor and acceptor molecules. We observe significant and persistent DDI strengths for a range of densities that map to ∼800 nm mean nearest-neighbor separation distance between donor and acceptor dipoles, a factor of ∼100 larger than free space. Our results pave the way to engineer and control long-range DDIs between an ensemble of emitters at room temperature.