Surface-Plasmon-Polariton-Assisted Diffraction of THz Waves on a Graphene-Covered Slit

Abstract

Transmission of plane electromagnetic wave through a tiny slit in a metal film covered by monolayer graphene is considered using a semi-analytical approach. We show that it gives rise to the diffraction accompanied by the excitation of standing waves of surface plasmon-polaritons in graphene, localized over the slit. These modes manifest themselves by characteristic peaks in the calculated absorption spectra in the THz range. It is shown that their spectral position depends on the refractive index of the material filling the slit and also can be tuned by the graphene doping level. Additionally, we clarify the physical nature of a low-frequency absorption band, which originates from the lowest order waveguide-type mode of the bare slit.