Optical pumping in graphene-based terahertz/far-infrared superluminescent and laser heterostructures with graded-gap black-PxAs1−x absorbing-cooling layers

We analyze the pumping of the graphene-based laser heterostructures by infrared radiation using the numerical model. To enable the injection of sufficiently cooled carriers into the graphene layer (GL) leading to the interband population inversion, we propose to use the graded-gap black-PxAs1  −  x absorption-cooling layers. Our calculations are based on the thermodiffusion-drift carrier transport model. We demonstrate that the proposed optical pumping method can provide an efficient injection of the cool electron–hole plasma into the GL and the interband population inversion in the GL. Since the energy gap in b-As layer can be smaller than the energy of optical phonons in the GL, the injected electron–hole plasma can be additionally cooled down to the temperatures lower than the lattice temperature. This promotes a stronger population inversion that is beneficial for realization of the GL-based optically pumped terahertz and far-infrared laser, plasmon emitters, and the superluminescent downconverters. We also compare the efficiency of optical pumping through the graded-gap and uniform absorbing-cooling layers.