Terahertz Waveguides by Coupling Plasmon Polaritons of Cylindrical Metal Wires and a Graphene-Embedded Slot Waveguide

Transmitting and processing terahertz (THz) signals in a chip-scale form are tremendously important due to extensive demands for these signals in various applications ranging from sensing, imaging, communication, and spectroscopy. However, developing compact and low-loss THz devices is still a challenging task. Herein, a novel waveguide structure consisting of a graphene-embedded slot waveguide sandwiched between two cylindrical metal wires operating in the THz range of f = 1-5 THz is proposed. By appropriately modulating the mode hybridizing from the graphene slot waveguide and cylindrical metal wires, the resultant mode obtains a long propagation distance of 192 mu m, while maintaining an ultrasmall mode area of 1.7 x 10(-4), thereby achieving an unprecedented high figure of merit (FoM) = 12 985. Compared with other reported structures, the proposed structure outperforms other reported structures in term of FoM, crosstalk, and fabrication difficulty. Furthermore, the degree of integration is evaluated by analyzing crosstalk between adjacent waveguides. With an edge-to-edge spacing of 2.7 mu m, the power transfer between waveguides can be ignored and the crosstalk is approximately frequency independent. It is believed that the proposed design paves an insightful approach into designing a wider variety of promising THz photonic integrated circuits.