Non‐linear optical properties of the band charge carrier gas

Abstract

AbstractA theory of non‐linear optical properties of a band charge carrier gas in semiconductors due to the influnece of a strong electromagnetic radiation on the probability of the carrier scattering by phonons or ionized impurities leading to intra‐band transitions is developed. A general expression for the polarization created by the carrier response in a laser field in the presence of a magnetic field and other electromagnetic fields (in particular, of a probe wave) is obtained at arbitrary temperatures using the path‐integral version of the density matrix method. The polarization spectrum is investigated. A self‐consistent set of wave equations is obtained to describe the propagation of electromagnetic waves, both, of those ones whose frequencies are determined by external sources and of those ones which are generated in the non‐linear medium under consideration. The explicit analytical expressions for a generalized dielectric permeability tensor and a generalized generation tensor are obtained for all principal scattering mechanisms and an arbitrary laser field intensity. The macroscopic (observable) manifestations of the polarization non‐linearity — the effects of the dependence of the absorption coefficient an the refractive index the intensity — are studied. The generation of harmonics and mixed frequencies is described; the influence of the generation on the laser wave propagation is investigated and found to be significant.