Theory of optical nonlinearities of coupled-band quantum wells with many-body effects

Nonlinear optical properties of lattice-matched and strained semiconductor quantum wells are computed using generalized optical Bloch equations. The equations combine the influence of many-body, strain and bandcoupling effects, within a consistent model for quasi-static screening that includes contributions from all occupied subbands in a single-plasmon-pole type approximation. Numerical solutions for the absorption and refractive index change of InGaAs-AlGaAs systems are presented in the quasi-equilibrium regime for a broad range of excitation conditions, from the low density excitonic regime to the highly excited gain region. Good agreement with recent experimental results is found.