DEGENERATE AND NONDEGENERATE 4-WAVE-MIXING IN SEMICONDUCTOR QUANTUM DOTS

We present wave-mixing techniques which are used to determine the tens or elements of the non-linear dielectric susceptibility, the dynamics of non-linear optical effects and the transport properties of a materi al. These techniques are applied to CdS nanocrystallites, prepared in a SiO2 matrix by a sol-gel method. They were prepared as thin films of variable density (up to 30% of volume). By the same experimental tech niques, porous silicon is studied and the results are compared to thos e obtained from luminescence and time-of-flight measurements.