  Graphene on hBN (G/hBN) has a long period moir\'{e} superstructure owing to
the lattice mismatch between two materials. Long periodic potential caused by
the moir\'{e} superstructure induces modulation of electronic properties of the
system. In this paper, we numerically calculate optical conductivity of G/hBN
under circularly polarized light irradiation. The lack of spatial inversion
symmetry in G/hBN induces the valley polarization. In further, the valley
polarization becomes most pronounced in the infrared and terahertz regions if
the twist angle between two materials is close to zero for non-doping case,
however, insensitive with twist angle for hole-doped case. These results will
serve to design the valleytronics devices using G/hBN.
