▎ 摘　　要

In this study, a new structure based on surface plasmon polariton propagation for decode operation in optical circuits is introduced. A graphene monolayer is sandwiched between two SiO2 layers for the terahertz wave transmission and a silicon ridge helps to achieve the high confinement. The concentration of the fundamental mode at the center of the plasmonic channel leads to a low loss and a long coupling length. By adjusting the graphene chemical potential at 0.1 eV and 0.5 eV, the surface plasmon polariton transmission is controlled, and realization of OFF and ON cases is possible for switching operation. The loss of 83.5 dB/mu m and 0.58 dB/mu m in response to the chemical potential of 0.1 eV and 0.5 eV confirms the ability of the designed structure for controlling the terahertz wave transmission. The area of the designed 2-to-4 decoder is almost 2.1 mu m2 smaller than all previous structures. This feature is highly needed in realizing optical integrated circuits. Besides, a long coupling length of 214.2 mu m, a contrast ratio of 36.43 dB, and a low cross-talk of -36.65 dB confirm the excellent performance of the proposed decoder. Compactness, low cross-talk, and high contrast ratio are the main advantages of the presented device.