Investigation of leaky and bound modes of graphene surface plasmons

Abstract

In this paper, the dispersion equation for TM polarized surface plasmon modes in the graphene layer embedded in a layered structure has been derived and numerically solved in THz frequencies (0.5–10 meV). Our model results show that this configuration, depending on the frequency region, can support both bound and leaky surface plasmons. Investigation of the supporting frequency region, electromagnetic field distribution, and propagation length of these two modes has been studied. Comparison of these modes with bound modes propagated in a graphene layer surrounded by two semi-infinite media shows that the propagation characteristics are strongly affected by the coupling effects of a high refractive index medium in its neighbor. The leakage of the power into this medium results in distinct decreasing of the propagation length in special frequencies which depend on the geometrical parameters. Additionally, the radiation efficiency depends on the frequency and it can be modified by the structure parameters. This radiation can be important in designing the plasmonic devices such as plasmonic antennas and may be applicable for light detection of surface plasmon polaritons.