Nonlinear optical properties of AlGaAs/GaAs multiple quantum well due to two-photon transitions between bound-to-continuum states

We have measured the anisotropic two photon absorption (TPA) of AlGaAs-GaAs MQW that exhibits a two-photon transition from confined-to-continuum states. We also have measured the anisotropic nonlinear refractive indices of AlGaAs-GaAs MQW. From the inspection of the TPA spectra and fitting the data, we found that the excitons resulting from two-photon transitions from confined-to-continuum states exhibit reduced binding energies and this is in good agreement with the theory.