▎ 摘　　要

A nonlinear metasurface made of a few-layer graphene and a metal grating is proposed in this work. It is demonstrated that the graphene plasmons can be excited in this configuration efficiently and two quite different kinds of resonances are found. The resonant behaviors and their origins are analyzed carefully, and the influences of grating groove and period on the resonances are discussed. It is surprising that the width of grating groove plays an important role in the resonant behaviors, distinct from the dielectric gratings. Due to the coupling of graphene plasmons and the grating, the highly tunability and large near field enhancement of our structure are observed. Finally, we apply our results to the optical bistability, and the low-threshold hysterical behavior with only a few MW cm(-2) is observed due to the large third-order nonlinear response of graphene and the strong localized field enhancement. We believe that our results will be inspiring not only for more complicated metasurfaces involving graphene, but also for other nonlinear optical applications.