▎ 摘　　要

Dynamic tuning of the plasmonic properties of graphene-based multilayer nanostructures provides a promising platform for the development of novel optoelectronic devices. In this paper, we numerically demonstrate that inserting an ultrathin dielectric buffer layer between monolayer graphene and a SiO2/Si substrate can result in highly tunable and confined low-loss mid-infrared surface plasmons. The characteristics of surface plasmons in the proposed device can be effectively controlled by changing the permittivity and thickness of the buffer layer, operation frequency, and chemical potential of graphene. In particular, we show that using nanometric buffer materials with dielectric constants lower than that of SiO2 can lead to a low propagation loss with better performance. In contrast, utilizing nanometric buffer materials with dielectric constants higher than that of SiO2 reduce the guided wavelength, resulting in a strong optical confinement. Moreover, increasing the operation frequency (chemical potential) leads to an increase (decrease) in propagation loss in the proposed structure. (C) 2016 Optical Society of America