Terahertz Amplification and Lasing in a Metal Groove with Active Graphene

Terahertz amplification and lasing via inversely populated graphene in a metal-dielectric groove resonator is studied theoretically. It is predicted that terahertz lasing arises in the vicinity of the cut-off frequency of the metal-dielectric groove resonator at Fabry–Perot resonances across the substrate slab due to the perfect matching of the characteristic admittance of the output waveguide and negative admittance of the terminal load (graphene on the dielectric substrate). Terahertz lasing arises for practical achievable value of the quasi-Fermi energy and realistic charge carrier relaxation time in graphene.