  We report stimulated Raman spectroscopy of the G phonon in both single and
multi-layer graphene, through Coherent anti-Stokes Raman Scattering (CARS). The
signal generated by the third order nonlinearity is dominated by a
vibrationally non-resonant background (NVRB), which obscures the Raman
lineshape. We demonstrate that the vibrationally resonant CARS peak can be
measured by reducing the temporal overlap of the laser excitation pulses,
suppressing the NVRB. We model the observed spectra, taking into account the
electronically resonant nature of both CARS and NVRB. We show that CARS can be
used for graphene imaging with vibrational sensitivity.
