Colloidal, "quantum-dot" semiconductormaterials, as exemplified by the sharp-cut yellow-red
filter glasses which contain small (less than 100 A diameter) crystallites of cadmium sulfide and/or
cadmium selenide, are of current interest because of the large near-resonant third-order nonlinear
optical response they exhibit. Because these semiconductors are generally soluble only in inorganic
media, such as silicate glasses, they have not been considered widely as candidates for inclusion in
organic polymer waveguides. We report here the initial results of a continuing study in which very small
colloidal particles of both cadmium sulfide and cadmium selenide (with crystallite diameters of typically
30-50 A) have been prepared by the reverse-micellar technique and then "capped" with a variety of
organic reagents, using the methodology described several years ago by Brus and Steigerwa1d14. By
varying the organic capping reagent, we find that we are able to produce significant variations in both
the solublilty and the nonlinear optical response of the resulting composite materials. In particular, we
find that the solubility of the particles in organic polymers such as PMMA and polycarbonate varies
greatly with the nature of the capping reagent, with corresponding changes in the nonlinear refractive
index of the composites. The feasibility of developing organic nonlinear optical waveguides based on
this approach will be discussed.
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