design and optimization of a graphene modulator based on hybrid plasmonic waveguide with double low-index slots

Graphene modulators based on surface plasmonic waveguides enable a strong interaction between light and graphene because great electric field enhancement occurs in the sub-wavelength region. however, a tight field confinement will cause a large metal absorption of light. thus, graphene modulator base on hybrid plasmonic waveguide has a tradeoff between the propagation loss and the modulation depth. here, we achieved a good balance between them by designing and optimizing an electro-optic modulator based on hybrid plasmonic waveguide with four graphene layers. the structure of the waveguide is metal/insulator/si/insulator/metal. the modulation depth and the propagation loss of the modulator are 0.524 and 0.05 db/μm respectively, which make a relatively high figure of merit about 10.5. also the obtained modulation bandwidth and power consumption are 150 ghz and 0.607 pj/bit, respectively.