Excitonic nonlinearities in wide gap II–VI multiple quantum wells

Abstract We report a comprehensive study of excitonic nonlinearities in Zn 1−x Cd x Se ZnSe multiple quantum wells under optical and electrical excitation. The stability of the heavy-hole exciton is studied as a function of Cd concentration by using pump and probe transmission spectroscopy. The heavy-hole exciton absorption peak is investigated as a function of the intensity of the pump beam until the exciton bleaching is reached. The experimental results are fitted with a theoretical model which includes band-gap renormalization, phase space filling and density dependent lifetime broadening. The correlation of these results with stimulated emission measurements performed also in magnetic field up to 8 T, allowed us to elucidate the role of excitons and free carriers in the lasing process in Zn 1−x Cd x Se ZnSe multiple quantum wells. Electric field induced effects are also studied in order to elucidate the role of quantum confined Stark effect on the optical modulation. Further insight in the nonlinear optical properties of excitons has been obtained by photoluminescence measurements under external bias.