Enhanced nonlinear optical properties of reduced graphene oxide decorated with silver nanoparticles

Reduced graphene oxide (rGO) decorated with silver nanoparticles (Ag NPs) is synthesized by femtosecond laser ablation in solution method. The nonlinear optical properties of both rGO and Ag NPs/rGO are measured using a femtosecond laser Z-scan technique. The results reveal that both the nonlinear absorption and nonlinear refraction in the hybrid are enhanced due to the interaction of the energy state of Ag NPs. The composite shows a saturation intensity 18.5 MW/cm2 and boosts the nonlinear refraction as large as 2~3 times of that of rGO reaching to -1.1 × 10-¹² m²/W. The enhancement of the saturable absorption might be caused by the further bleaching the valence band of rGO due to the transfer of the light excited carriers from graphene to the metal state of the NPs. The slow relaxation of the excited carriers to the ground state of rGO will also cause the increase of the carrier density and thereby result in the enhancement of the nonlinear refractive index of the material.