Three-photon absorption coefficients in ZnSe/ZnS0.18Se0.82 strained-layer superlattices

We provide the first experimental determination of three-photon absorption (ThPA) coefficients α(3) in a quasi-bidimensional structure. The measurements of α(3) have been performed on a sample of a ZnSe/ZnS0.18Se0.82 strainedlayer superlattice at fixed excitation energies corresponding to the exciton resonances near the direct band gap. The evidence of the ThPA process in such energy range points out the huge enhancement of exciton non-linearities in quantum-confined systems.