Design and simulation of a subwavelength 4-to-2 graphene-based plasmonic priority encoder

Abstract

In this paper, a plasmonic waveguide including a sandwiched SiO2 channel between a graphene layer and a silicon ridge is designed. The surface plasmon polaritons are concentrated near the graphene and propagate along the graphene-SiO2 interface. By adjusting the chemical potential of graphene at 0.1 eV and 0.5 eV, the propagation loss of 486.3 dB/μm and 0.42 dB/μm is obtained for designing a plasmonic switch. The figure-of-merit for the designed waveguide is equal to 160. By getting the help of 6 waveguides and 2 combiners, a 4-to-2 plasmonic priority encoder is proposed. If two input signals are synchronously applied to an encoder, the priority feature is needed for corresponding to the higher priority input and providing the correct binary code at output ports. Considering the priority for inputs, all working states in four categories are simulated and the performance of the designed encoder is evaluated. The contrast ratio of 13.1 dB and the cross-talk of −16.22 dB are obtained for the working wavelength of 7 µm. The area of the presented encoder is 1.92 μm2, smaller than other works, promising for optical integrated circuits.