Exact solution for square-wave grating covered with graphene: Surface   plasmon-polaritons in the THz range
  We provide an analytical solution to the problem of scattering of electromagnetic radiation by a square-wave grating with a flat graphene sheet on top. We show that for deep groves there is a strong plasmonic response with light absorption in the graphene sheet reaching more than 45%, due to the excitation of surface plasmon-polaritons. The case of grating with a graphene sheet presenting an induced periodic modulation of the conductivity is also discussed. 
N. M. R. Peres, Yuliy V. Bludov, A. Ferreira, Mikhail I. Vasilevskiy
cond-mat.mes-hall