Strong Coupling of Nanoplatelets and Surface Plasmons on a Gold Surface

Nanoplatelets are strongly anisotropic colloidal nanocrystals confined in only one direction. Perfect thickness control and large lateral dimensions enable a large exciton coherence area that exhibits a high oscillator strength. Here we investigate experimentally the existence of a strong plasmon exciton coupling regime in a system consisting of a layer of nanoplatelets on top of a gold planar surface. We performed reflectivity measurements to extract geometrical and optical parameters of the system, and we used them to calculate numerically the modes and obtain the dispersion relation of the structure. Our results show a clear Rabi splitting between an upper and a lower polariton branch, thus demonstrating unambiguously that the system is in the strong coupling regime.