Controlling Single-Emitter Strong Coupling by Sculpting DNA Dye Scaffolds in NPoM Cavities

Coherent coupling of light and single molecules enables the development of next-generation room temperature-capable nanophotonic devices. Small mode-volume optical fields can be achieved with plasmonics, but challenges remain in placing oriented emitter molecules inside plasmonic cavities to access strong coupling consistently in emission. Using DNA origami, single-emitter molecules can be aligned inside subnanometric cavities created between a gold nanoparticle and a gold mirror. We observe that the exact design of DNA scaffolding architecture surrounding a cyanine dye changes how its emission couples to the nanocavity, as well as how Au atoms respond to the optical forces, leading to continuous tuning of the dominant plasmonic mode. Through this, we show how strong coupling between three different dyes and the plasmon resonance always leads to low-energy light emission, independent of detuning.