  On the basis of the Kubo formula we evaluated the optical conductivity of a
graphene sheet. The full behavior of frequency as well as temperature
dependence of the optical conductivity is presented. We show that the
anisotropy of conductivity can be significantly enhanced at high frequencies.
The photon absorption depends on the field polarization direction. At the
frequency comparable to the maximum separation of upper and lower bands the
photon-induced conduction of electrons is strongly suppressed if the
polarization of field is along the zigzag direction. The corresponding optical
conductivity is several orders of magnitude weaker than that when the light is
polarizing along the armchair direction. We propose that the property of
orientation selection of absorption in the graphene can be used as a basis for
a high-frequency partial polarizer.
