An electro-optical full-subtractor using hybrid-integrated silicon-graphene waveguides

In this paper, an electro-optical full-subtractor composed of cascaded Mach-Zehnder interferometer-based silicon-graphene switches is designed and analyzed. To achieve high-speed switching function, electrical signals are applied to adjust the chemical potential of graphene and change the permittivity of graphene, leading to the variation of the effective index of the silicon-graphene waveguide used as the phase shifter. Calculation results show, at the wavelength of 1550 nm, the extinction ratio of the designed device larger than 49.6 dB are obtained with an operating speed of 10Gbit/s.