Quasiequilibrium nonlinearities in Faraday and Kerr rotation from spin‐polarized carriers in GaAs Free

Semiconductor Bloch equations (SBEs), which microscopically describe optical properties in terms of the dynamics of a Coulomb interacting, spin‐unpolarized electron‐hole plasma, can be solved in two limits: the coherent and the quasiequilibrium regimes. Recently, Nemec et al. [1] reported circularly polarized pump‐probe absorption spectra in the quasiequilibrium regime for carrier spin‐polarized bulk GaAs at room temperature, which lacked a suitable microscopic theoretical understanding. We have very recently explained their results by solving the spin‐SBEs in the quasiequilibrium regime (spin‐Bethe‐Salpeter equation), and accounted for spin‐dependent mechanisms of optical nonlinearity [2]. Here, we extend our theory to the microscopic calculation of Kerr and Faraday rotation in the quasiequilibrium regime, for which there are no experimental or theoretical results available.