  We consider a graphene sheet encapsulated in a two-dimensional metallic
grating and a substrate ($\mathrm{Al_{2}O_{3}}$) and subjected to an external
magnetic field (in Faraday configuration). The grating consists of a thin
perfectly conducting metal film perforated with a 2D periodic array of square
holes. According to our calculations, significant changes in the spectra of the
Faraday rotation angle of the transmitted wave and of the magnetic circular
dichroism should be expected in this situation compared to bare graphene. We
explain this enhancement by the excitation of graphene magnetoplasmons that
accompanies the transmission of the electromagnetic wave through the structure.
The results can be interesting for applications in THz photonics, such as
switchable rotating polarizer and optical isolator.
