Linear and nonlinear optical properties of AgNPs and AgNPs/graphene composites modulated by localized surface plasmon resonance effect

The localized surface plasmon resonance (LSPR) properties of metal particles can be affected by their surrounding media, and the LSPR properties affect the optical properties of metal particles and their composites. However, this indirect influence of the surrounding media on optical properties is often ignored. In this regard, we have synthesized silver nanoparticles (AgNPs) and AgNPs/graphene composites, and investigated the linear and nonlinear optical properties affected by the LSPR effect that was controlled by the surrounding media of AgNPs. The structure and morphology characterization showed that the size of AgNPs and their distribution on graphene were uniform. The distribution and enhancement of the local field around the AgNPs were studied using the finite-difference time-domain (FDTD) method. The nonlinear optical properties were measured using the Z -scan technique. The results show that as the refractive index of the surrounding modification layer of AgNPs was adjusted from 1.4 to 2.5, the LSPR peak of AgNPs was redshifted more than 30 nm, the linear absorption of AgNPs/graphene was also slightly redshifted. Moreover, when the refractive index was increased to 1.9, the reverse saturation absorption of AgNPs and the saturation absorption of AgNPs/graphene both reached their maximum values, and then decreased. This investigation provides a different way to modulate optical properties of materials for possible applications in photonic devices via the appropriate LSPR effect controlled by the refractive index of the modification layers.