  Using carefully designed hybrid metal-dielectric resonators, we study
molecular optomechanics in the strong coupling regime ($g_{\rm }^2/\omega_m {>}
\kappa$), which manifests in anharmonic emission lines in the sideband-resolved
region of the cavity-emitted spectrum ($\kappa{<}\omega_m$). This nonlinear
optomechanical strong coupling regime is enabled through a metal-dielectric
cavity system that yields not only deep sub-wavelength plasmonic confinement,
but also dielectric-like confinement times that are more than two orders of
magnitude larger than those from typical localized plasmon modes. These hybrid
metal-dielectric cavity modes enable one to study new avenues of quantum
plasmonics for single molecule Raman scattering.
