▎ 摘　　要

In this work, nanowire-based symmetrical graphene hybrid plasmonic waveguides for possible broadband optical modulation have been proposed. The full-vectorial finite element method has been employed to analyze the modal properties and modulation characteristics of the proposed structures. The fundamental supermode supported by these geometries is evolved from a near-field coupling between metallic and dielectric nanowires. Here, the strong optical capacitance effect in the low-index dielectric gap region has been exploited to enhance light-graphene interaction in the subwavelength device size. Thus, the optical absorption of graphene significantly increases. Therefore, the structures even with their small footprints offer a very high extinction ratio and small energy consumption per bit (as low as 0.9 fJ/bit), simultaneously with appreciably high modulation bandwidth at the telecommunication wavelength. A substantially small variation of modulation performance for a broad range of operation wavelength and gap widths suggest their broadband operability. Furthermore, the modulation performance has been studied incorporating the optical anisotropy of graphene. Thus, the proposed waveguides show a good promise in high-speed broadband optical modulation. (C) 2020 Optical Society of America