ABSTRACT
Composites made from small semiconductor or metal clusters isolated in a variety of insulating matrices have provided materials in which a wide variety of nonlinear processes may be observed. However, numerous additional nonlinear optical (NLO) effects have also been observed, including exciton bleaching processes, and enhanced optical susceptibility from superradiant exciton recombinations mediated by the quantum size confinement of the semiconductor clusters. The quantum confinement effects and nonlinear optical processes associated with metal cluster-insulator composites seem to be related to shifts in the plasma resonance, with the NLO activity resulting from an enhanced optical Kerr effect. This chapter describes briefly the various nonlinear optical processes of particular relevance to quantum-confined semiconductor and metal clusters, and the various measurements conducted. The ideal semiconductor-glass composite would consist of a single element or stoichiometric binary semiconductor whose size can be varied but yet can maintain a very narrow distribution of crystal sizes. Intense photoluminescence has been observed in semiconductor-glass composites.
