▎ 摘　　要

We study the nonlinear optical response of graphene in nanostructures. The spherical nanoparticle coated with a monolayer of graphene displays enhanced optical Kerr nonlinearity and, consequently, optical bistability and multistability in a broad range of incident optical intensity. This optical bistability significantly appertains on the geometry of the shell-coated nanoparticle, the fractional volume of the metallic core, as well as the core genre and Fermi energy of graphene. In particular, Fermi energy could also affect the optical bistability and induce switching from optical bistability to optical multistability. Due to the importance of core-shell nanoparticles, this model may find potential applications in optical bistable devices such as all-optical switches, optical transistors, and memories. (c) 2018 Optical Society of America