Design of symmetric graphene-based hybrid plasmonic nanowaveguide with strong confinement and high efficiency in the mid-infrared spectrum

In this paper, a unique symmetric graphene-based plasmonic nano-waveguide is proposed to guiding electromagnetic waves in the mid-infrared spectrum. The geometric structure of the waveguide consists of two symmetrical cylinders arranged around a rectangular substrate with a high refractive index. The lateral surfaces of both cylinders are covered with a graphene monolayer, and the cylinders and rectangular substrate are placed in a low refractive index environment. Here, the modal model properties of surface plasmon polaritons are investigated using the finite element method. The dependence of the propagation properties of the modes on the frequency of the incident wave, the graphene Fermi energy and the dimensions of the geometric structure of the waveguide has been calculated in detail. Due to the unique structure of the designed waveguide, the propagation length of the modes is approximately 4600 nm , the normalized mode area is ~〖10〗^(-6) and the figure of merit is nearly 500. According to the simulation results, this structure has a strong confinement the light subwavelength and high performance in the mid-infrared region for use in practical applications in photonic integrated circuits.