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.
