Graphene active plasmonics for new types of terahertz lasers

This paper reviews recent advances toward new types of terahertz (THz) lasers using active plasmonics in graphene. Optical gain originated from graphene ultrafast nonequilibrium carrier dynamics and phonon properties in the broadband THz frequency range might pave the way for the THz lasers but the challenge is to overcome the strong losses in the THz range. Graphene plasmons, quanta of the collective charge density waves excited by the two-dimensional carriers in graphene, can substantially enhance the light-matter (THz photons-graphene) interaction, leading to a "giant THz gain". One possible implementation relies on superradiant plasmonic THz lasing in graphene-metal micro-ribbon array structures.