Toward the Creation of Graphene Terahertz Lasers

Abstract

This paper reviews recent research advances toward the creation of graphene terahertz (THz) lasers. Graphene, a monolayer carbon-atomic honeycomb lattice crystal, has attracted attention due to its superior optoelectronic properties that reflect its massless and gapless energy spectrum. So far we have theoretically and experimentally revealed the occurrence of amplified stimulated THz emission due to negative dynamic conductivity in optically pumped graphene, which will lead to new types of THz lasers. Optical pumping with rather high photon energy of the order of“ ~eV” significantly heats the carriers, which dramatically increases the pumping threshold, preventing population inversion. Current injection pumping is the best solution because electrical pumping can serve any pumping energy, even under the order of“ meV” when a p-i-n junction is formed like semiconductor laser diodes. Dual gate structures can make a p-i-n junction in the graphene channel.