  The combination of graphene with noble-metal nanostructures is currently
being explored for strong light-graphene interaction enhanced by plasmons. We
introduce a novel hybrid graphene-metal system for studying light-matter
interactions with gold-void nanostructures exhibiting resonances in the visible
range. Strong coupling of graphene layers to the plasmon modes of the nanovoid
arrays results in significant frequency shifts of the underlying plasmon
resonances, enabling more than 30% absolute light absorption in a single layer
of graphene and up to 700-fold enhancement of the Raman response of the
graphene. These new perspectives enable us to verify the presence of graphene
on gold-void arrays and the enhancement even allows us to accurately quantify
the number of layers. Experimental observations are further supported by
numerical simulations and perturbation-theory analysis. The graphene gold-void
platform is beneficial for sensing of molecules and placing R6G dye molecules
on top of the graphene, we observe a strong enhancement of the R6G Raman
fingerprints. These results pave the way toward advanced substrates for
surface-enhanced Raman scattering (SERS) with potential for unambiguous
single-molecule detection on the atomically well-defined layer of graphene.
