Proposed Graphene Nanospaser

We show that graphene monolayer coupled to multi-quantum well system can form a graphene spaser, which is a coherent quantum generator of surface plasmons in graphene. The active element of graphene spaser is a multi-quantum well system with a design similar to the design of an active element of quantum cascade laser. Under realistic parameters of the multi-quantum well system, the spasing in graphene monolayer can be achieved at a finite doping of graphene and at a plasmon frequency, 0.15 eV, close to the typical frequency of intersubband transitions in multi-quantum well systems.