Active guiding of Dirac plasmons in graphene

The Dirac plasmon propagation in active pristine graphene with the carrier population inversion created by the diffusion of the photoexcited carriers from a semiconductor substrate is studied theoretically. It is shown that an order of magnitude smaller pump power can be used for the diffusion pumping as compared to direct optical pumping of graphene for obtaining the same plasmon gain in graphene. We find that the field of the amplified plasmons remains strongly confined in the vicinity of graphene similarly to the case of the attenuated plasmons. Remarkably, the diffusion pumping is characterized by low insertion losses due to small photoexcited carrier concentration in the carrier-supplying semiconductor substrate in the region of the plasmon field confined near graphene.