Optical nonlinearities in mixed type I–type II GaAs/AlAs multiple quantum wells

We demonstrate all-optical nonlinearities at low cw pump powers (mW/${\mathrm{cm}}^2$) using a GaAs/AlAs double-quantum-well design that spatially separates photoexcited electron-hole pairs. The nonlinearities are examined over a range of temperatures and in a variety of samples. Theoretical calculations based on many-body interactions are in good agreement with the measured spectra and have been used to improve the structure design.