3RD-ORDER NONLINEAR SUSCEPTIBILITY IN GAAS ALXGA1-XAS SUPERLATTICE WITH A SPECIAL LAYERED STRUCTURE

By taking into account the nonparabolic band structure of the constitu ents and the coupling between the periods, we calculated the triply re sonant nonlinear susceptibility in a specially designed GaAs/AlxGa1-xA s superlattice. It consists of infinite repeated periods, each of whic h is an alternative stacking of GaAs and AlxGa1-xAs layers with specia l layer thicknesses, designed in such a way that the minibands of the superlattice are nearly equally separated. The triply resonant suscept ibility is produced by a three-photon process. In some cases coupling between the periods may slightly enhance the magnitude of the third-or der susceptibility. Possible ways of maximizing the nonlinear suscepti bility of the superlattice are also discussed.