Effects of the fermi level of graphene on the leaky surface plasmon waves of graphene

Coupling of graphene surface plasmons to far-field radiation can be important in designing reconfigurable THz radiating devices. Coupling of these modes into the far field radiation is possible via a high refractive index medium near the graphene. Such layered structures are capable to support the leaky surface plasmon modes. Characteristics of these leaky-type modes depend on the structure s geometrical parameters. In this study, we investigate the effects of the fermi level of graphene on the radiation efficiency and radiation pattern of leaky-type graphene surface plasmon polaritons. Numerical solutions of dispersion equation of leaky surface plasmon modes of graphene in the considered structure, show that increasing the fermi level leads to a change in radiation efficiency depending on frequency region. Additionally, the radiation pattern gets sharper and the peak position pulls toward low angles by increasing the fermi level. These tunable characteristics of radiation efficiency and radiation pattern can be used in reconfigurable THz devices.