Optical nonlinearities in strained-layer InGaAs/GaAs multiple quantum wells

Optical nonlinearities in strained‐layer InGaAs/GaAs multiple quantum wells (MQWs) are studied using pump‐probe spectroscopy. It is found that the carrier density required for absorption saturation in a strained InGaAs/GaAs MQW is about a factor of two lower than that in an unstrained GaAs/AlGaAs MQW with similar structures, while the nonlinear index change per carrier is about the same for both samples. The decrease in the saturation density in the strained MQW is explained by the increase of the top valence‐band curvature caused by the compressive strain in the quantum well