Free exciton emission and optical nonlinearity of ZnSe-ZnS/CaF2 superlattices under high excitation density

The free exciton emission and optical nonlinearity in ZnSe-ZnS grown by MOCVD on CaF 2 substrates have been studied under different excitation densities at 77 K. We report the first observation of the new emission band due to Ex − Ex interaction, exciton saturating absorption and exciton optical bistability in ZnSe-ZnS/CaF 2 superlattices. The dominant exciton optical nonlinear mechanism for ZnSe-ZnS/CaF 2 superlattices under high excitation density is the combination of phase-space filling of exciton state and exciton band broadening