Tunable Strong Light-matter Interaction in Plasmonic Nanocavities

Probing the strong coupling between quantum emitters and an optical cavity is crucial to both fundamental studies in cavity-quantum electrodynamics, as well as potential applications such as quantum information processing, low threshold lasing and ultrafast single-photon switching. Compared to conventional dielectric cavities, plasmonic nanocavities have the advantage of ultra-small mode volumes and tunable resonances. In this work, we report the observation of strong coupling between dye molecules and film-coupled plasmonic nanocavities. A large splitting energy up to 160 meV is achieved at room temperature. Additionally, a distinct anti-crossing behavior with two prominent branches has been observed when tuning the plasmon resonance, which is a signature of the presence of strong coupling. Moreover, we show that the coupling strength can be tuned by varying the number of molecules that are coupled to the plasmonic cavity or by changing the dimensions of the cavity. Integrating these hybrid nanostructures with active materials is promising for the design of novel active nanophotonic devices operating at room temperature.