  We theoretically demonstrate that a system formed by a drift-current biased
graphene sheet on a silicon carbide substrate enables loss compensation and
plasmon amplification. The active response of the graphene sheet is rooted in
the optical pumping of the graphene plasmons with the gain provided by the
streaming current carriers. The proposed system behaves as an optical amplifier
for the plasmons co-propagating with the drifting electrons and as a strong
attenuator for the counter-propagating plasmons. Furthermore, we show that the
feedback obtained by connecting the input and output of the system, e.g., as a
ring-shaped graphene - silicon carbide nanoresonator, combined with the optical
gain provided by the drifting electrons, may lead to spasing.
