Quantum size effects on the third order optical nonlinearity of CdS quantum dots in Nafion

Optical nonlinearities of CdS quantum dots in the strongly confined regime are probed through degenerate four-wave-mixing experiments in an attempt to study the size dependence of the third order optical susceptibility chi ((3)). The results indicate that chi ((3)) is strongly dependent on the diameter of the dots and that there is a large increase in chi ((3)) values as the diameter decreases below 2 nm. Polarization discrimination studies point to nonthermal contributions to the mechanism of optical nonlinearity. (C) 2000 Elsevier Science B.V. All rights reserved.