▎ 摘　　要

The application of graphene and graphene-like materials in photonics has attracted extensive attention in recent years. However, their nonlinear optical (NLO) properties need to be improved urgently. Herein, we demonstrate a method to improve the NLO properties of reduced graphene oxide (RGO) via the decoration of Ni transition element doped ZnS nanoparticles on RGO sheet. The samples of Ni doped ZnS decorated RGO (Ni-ZnS/RGO) composites with different Ni doping concentrations and ZnS particles sizes were synthesized via a facile solvothermal method. The NLO responses of Ni-ZnS/RGO composites were investigated via the Z-scan technique under a picosecond laser at 1064 nm. The results indicated that Ni-ZnS/RGO composites exhibited saturation absorption and positive nonlinear refraction properties, and they could be adjusted by controlling the doping concentration of Ni and the size of ZnS nanoparticles. The maximum saturation absorption coefficient, nonlinear susceptibility and nonlinear refractive index of Ni-ZnS/RGO among all the samples were obtained to be- 2.5 x 10(-10) mW(-1), 3.2 x 10(-13) cm(2)/W and 14.1 x 10(-14) cm(2)/W, which were 25, 18 and 23 times of those of RGO, and 3.6, 11.7 and 4.2 times of those of ZnS doped with 2.5%Ni, respectively. They were also much greater than those of the direct sum of the two independent units, RGO and Ni-doped ZnS. These highly improved NLO responses of Ni-ZnS/RGO composites were ascribed to the inhibition of the direct electron-hole recombination due to the introduction of Ni doped impurity energy levels within the band gap of ZnS, as well as the charge transfer and synergism between ZnS and RGO. The results of this investigation may promote the development and applications of Ni-ZnS/RGO materials in photonic devices.