Quasiclassical and quantum radiation in graphene

We consider the kinetics of a linearly polarized, spatially homogeneous, quasiclassical electric field passing through graphene within the Narozhny–Nikishov model. We obtain optical coefficients (of absorption, reflection, and transmission) numerically and analytically as functions of the field amplitude and duration. We analyze the range of applicability of the Dirac approximation using a parameter θ , which represents the ratio of the quasielectron energy to the quantum energy of the external field. We numerically obtain the energy of quantum radiation produced by the electron-hole plasma.