Molecules in plasmonic nano-cavities

Plasmonic nano-cavities have the ability to confine light in sub-wavelength gaps. The smallest possible plasmonic nano-cavities are achieved with the nanoparticle on mirror (NPoM) configuration [1], where a flat metal substrate is separated from a nanoparticle with a thin molecular spacer, typically of 1–1.5nm thick (Fig.1a). The massive field enhancement facilitates the strong-coupling of a single molecule with a plasmon mode at room temperature, as we recently demonstrated [2]. Here, we discuss the complex behaviour of plasmonic nano-cavities and the dissociation between the near-field interacting with the molecule and the far-field spectra measured experimentally.