A graphene-on-gap modulator with high modulation efficiency

We propose a high efficient graphene-on-gap modulator (GOGM) by employing the hybrid plasmonic effect, whose modulation efficiency is ∼8-folds larger than that of present graphene-on-silicon modulator (GOSM) (∼0.1 dB / μm). The proposed modulator has the advantage of short modulation length ∼3.6 μm, relatively low insertion loss ∼0.32 dB and larger modulation bandwidth ∼0.48 THz. Moreover, an efficient taper coupler has been designed to convert the quasi-transverse electric (TE) mode of conventional silicon waveguide to the hybrid plasmonic mode of GOGM, with a high coupling efficiency of 91%. This study may promote the design of high-performance on-chip electro-optical modulator.