Optical limiting and nonlinear optical properties of gold-decorated graphene nanocomposites

Although metal nanoparticle-decorated nanomaterials exhibit excellent optical limiting (OL) performance at a relatively higher fluence (\textgreater 9 J/cm$^{2})$, there is a dearth of OL materials for protecting low damage threshold (\textless 1 J/cm$^{2})$ photonic devices. The rehybridization of some metal $d$-orbitals and graphene $p$-orbitals often leads to undesirable changes in graphene's electronic structure, which adversely affects OL. Here, we demonstrate that $d$-orbitals of Au nanoparticles exhibit little or no rehybridization with graphene, and result in an enhanced OL behavior even at a low fluence of $\sim$ 0.4 J/cm$^{2}$ due to the excellent photo-absorption of Au combined with rapid carrier thermalization by graphene.