▎ 摘　　要

In this paper, we present subwavelength half-subtractor and half-adder circuits based on graphene plasmonic waveguides. Surface plasmon polaritons are stimulated by an incident TM wave with a wavelength of 13.8 mu m in graphene-insulator-metal structures. Using graphene provides high confinement, low loss, and flexibility in controlling light propagation. Simulations show that the proposed half-subtractor has contrast ratios as high as 10.60 dB and 15.75 dB for difference and borrow bits, respectively. This structure calculates A-B and B-A, simultaneously. Also, the results indicate that the contrast ratios for sum and carry signals of the half-adder are 7.4 dB and 14.83 dB, respectively. The footprints of the half-subtractor and half-adder are 0.315 mu m(2) and 0.640 mu m(2), respectively, which denote the compact sizes of the structures. Owing to the high contrast ratio and ultra-compact size, the presented circuits are expected to be used widely in photonic combinational integrated circuits.