  Graphene is considered to be plasmon active only up to the infrared based on
combined tight binding model and random phase approximation calculations. Here
we show that the optical properties of graphene as measured by ellipsometry and
simulated by density functional theory imply the existence of strongly
localized graphene plasmons in the visible with a line width of 0.1 eV. Using
small emitters that provide the high wavevectors necessary to excite graphene
plasmons at optical frequencies we demonstrate graphene plasmon induced
excitation enhancement by nearly 3 orders of magnitude.
