Realization of electro-optical decoder, half-adder, and half-subtractor using graphene plasmonic waveguides

In this paper, two novel electro-optical decoders based on graphene-dielectric-metal waveguides are proposed for use in the infrared region. The use of graphene instead of noble metals improves the efficiency of the device due to higher confinement, lower losses, and the capability of controlling the propagation of light via electrostatic doping. Simulation results demonstrate that the minimum extinction ratio is more than 36 dB for the proposed 2 x 4 decoder. The footprint of this decoder is 8 mu m(2) which represents an ultra-compact structure. By following the design rules, a 3 x 8 decoder with a minimum extinction ratio of 23 dB and a footprint of 29 mu m(2) is presented. Also, the proposed structure can act as a simultaneous half-adder/subtractor circuit by applying some changes. The Sum and Carry bits have extinction ratios of 24.66 dB and 28.2 dB, respectively. The half-subtractor part of the circuit calculates two X-Y and Y-X subtraction operations simultaneously. The minimum extinction ratios of Difference and Borrow bits are 22.39 dB and 25.98 dB, respectively. Also, the footprint of the half-adder/subtractor circuit is less than 33 mu m(2).