Theory of nonlinear optical absorption in coupled-band quantum wells with many-body effects

Nonlinear optical absorptionspectra and refractive index changes are computed for coupled‐band semiconductorquantum wells by numerically solving the interband polarization equation. The theory combines band‐structure engineering with many‐body techniques and is applied to lattice‐matched GaAs‐AlGaAs and strained InGaAs‐GaAs systems with carrier densities ranging from the excitonic to the gain regimes. Good agreement with recent experimental results is found.