Optical pumping through a black-As absorbing-cooling layer in graphene-based heterostructure: Thermo-diffusion model

We study the optical near- and mid-infrared pumping of the heterostructure based on graphene with a black-As layer. This layer serves for the optical generation and cooling of the electron-hole pairs to be injected into the graphene layer. Due to the cooling of the electron-hole pairs, their energy in the case of the absorbing-cooling layer with the optimized thickness can be close to the energy gap of the black-As layer. Owing to a relatively narrow energy gap of the black-As layer Δ_G, the energy of the injected electron-hole pairs can be smaller than the energy of optical phonons in in graphene (hω₀ ≃ 0.2 eV. This can provide the formation of the cold electron-hole plasma in the graphene-layer that is beneficial for achieving of the interband population inversion and the interband terahertz lasing. The obtained results can be used for the optimization of the terahertz lasers with the optical pumping.