Small footprint symmetrical graphene hybrid plasmonic waveguides for high-speed broadband optical modulation

Abstract

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.