Optical reversible logic gates based on graphene-silicon slot waveguides

Abstract In this paper, three optical reversible logic gates including Toffoli, Peres and Fredkin gates utilizing graphene-silicon slot waveguides are presented and investigated. The introduced Toffoli, Peres and Fredkin gates are consisting of cascaded Mach-Zehnder interferometers and multimode interference couplers. In each Mach-Zehnder interferometer, graphene-silicon slot waveguides are designed to be phase shifters. As the chemical potential varies, a big change in the real part of the effective refractive index of our designed graphene-silicon slot waveguide would be formed, and thus relatively compact and broadband Toffoli, Peres and Fredkin gates are achieved. At 1550 nm, when the chemical potential varies from 0.60 to 0.90 eV, 3-dB bandwidth of 20.84 GHz,Vπ • Lπof 40.46 V•μm and 0.40 pJ/bit energy consumption can be obtained for the designed graphene-silicon slot waveguide with 5-nm-thick ZrO2spacers. For the corresponding Toffoli, Peres and Fredkin gates, the minimum extinction ratios are 24.19, 24.60 and 18.63 dB and the maximum crosstalks are -32.56, -27.81, and -20.80 dB, respectively.