  We investigate the nonlinear optical features of a graphene sheet embedded in
an active cavity and we show that, when tuned near its lasing threshold, the
cavity is able to isolate the spatially localized graphene nonlinearity thus
producing a very strong nonlinear device response with multi-valued features.
As opposed to standard situations where the small thickness of the graphene
sheet hampers its remarkable nonlinear optical properties to be exploited, in
our scheme the strong nonlinear optical regime is mainly triggered by the very
intrinsic planar localization of graphene nonlinearity. The proposed strategy
for exploiting graphene nonlinearity through its unleashing could open novel
routes for conceiving ultra-efficient nonlinear photonic devices.
