Graphene-supported tunable waveguide structure in the terahertz regime

The tunable waveguide properties of the graphene supporting structure Si -SiO sub(2) -graphene-dielectrics-graphene-SiO sub(2)- Si (SiSiO sub(2) GDGSiO sub(2) Si) have been investigated in the terahertz regime by using the finite element method (FEM) and transfer matrix method (TMM). The study shows that the numerical results obtained from FEM and TMM agree well. The contour results show that as the frequency increases, the effective index increases, and the loss shows a peak; with the increase in the Fermi level, the effective index decreases, and the loss decreases. With a smaller effective mode area, the confinement of the SiSiO sub(2) GDGSiO sub(2) Si structure is much better than that of the Si-dielectrics-graphene-dielectrics-Si structure. The propagation properties of the structure can be modulated by using the applied gate voltage. The modulation depth of the propagation losses can reach more than 90%. The results are helpful to the design of tunable graphene optoelectronic devices, such as polarizers, modulators, and metamaterial devices.