ABSTRACT
In this chapter, the authors put forward and optimize the surface plasmonic metal waveguide geometry for the recently proposed terahertz (THz) injection laser based on resonant radiative transitions between tunnel-coupled graphene layers. They find an optimal number of active graphene layer pairs corresponding to the maximum net modal gain. The authors introduce a scheme of THz laser based on resonant photon-assisted transitions in multiple graphene layer structure embedded in a surface plasmonic waveguide enhancing the light-matter interactions. They find the ultimate modal gain and threshold length for lasing, and show that a seemingly simple solution to increase the number of active graphene layer pairs does not always lead to the gain enhancement. The authors find the corresponding upper limit of the modal gain in the THz lasers based on the multiple tunnel-coupled GLs. Our findings support the possibility of creating ultracompact graphene-based THz lasers.
