Left: (a) sketch of the tuned photonic crystal cavity, with lattice constant  nm. Right: (b) sketch of the suspended graphene/ silicon membrane. Top right inset: Dirac cone illustrating the highly doped Fermi level (dashed blue circle), allowing the two-photon transition (blue arrows) but forbidding the one-photon transition (red dashed arrow). Bottom right inset: computed Ey-field along the -direction, with graphene at the evanescent top interface.