Switching of terahertz plasmon propagating direction in a dual layer graphene with periodic grating gate

Switching of terahertz plasmon propagation direction in a periodic graphene structure with a double grating gate is studied theoretically. The coefficient of transformation of an incident electromagnetic wave into a propagating plasmon is numerically calculated. It is shown that near the “radiative” and “nonradiative” mode crosses plasmons propagating can be switched between forward and backward directions with respect to the x-axis by tuning voltage values applying to sub-grating gates. The absolute value of the transformation coefficient can exceed the unit value because of the gain provided by the active graphene.