Nonlinear optical properties and ultrafast response of GaAs-AlAs type-II quantum wells

Femtosecond and CW optical nonlinearities associated with the spatial separation of electrons and holes in GaAs--AlAs type-II quantum wells are reported. Without applied electric field, the nonlinearities due to blue shift and bleaching of the heavy-hole exciton resonance are observed. An applied static longitudinal electric field changes these nonlinearities through the redistribution of electrons. Furthermore, optical nonlinearities and even gain for ultrahigh excitation conditions in type-II structures are reported and compared to those in similar type-I structures. In this paper the theoretical framework used for modeling the type-II system in the presence and absence of electrons is described