Optical Properties

Abstract

The linear response to a time-dependent adiabatic external perturbation as well as the equilibrium linear response are presented. The specific relationships of the longitudinal dielectric response of an electron–hole plasma to the density–density correlation function depending on the explicit inclusion of the Coulomb interaction between the charged particles are explained. The dielectric function is explicitly calculated within the Hartree approximation. The response to a transverse (propagating) electric field within a simple model of a semiconductor with s-type conduction and p-type valence bands including the Coulomb attraction between the created electron–hole pair leads to the Elliot-formula containing the exciton peak, as well as the Coulomb-enhancement. Some discussion is devoted also to a modern branch of optical experiments with ultra-short and intense laser beams. The so-called semiconductor Bloch equations are derived and a third order non-linear approach to differential transmission (DTS) and four wave mixing (FWM) is developed.