Large Enhancement of Third-Order Optical Susceptibility in CuCl Quantum Dots Embedded in Glass

We report third-order optical nonlinearity of CuCl microcrystallites with radii of 1.5-8.0 nm in glass. We measured absolute values of third-order susceptibility χ(3) using degenerate four-wave mixing and imaginary χ(3) by absorption saturation measurements. The highest value of χ(3) was obtained to be 2×10-6 esu for microcrystallites with the mean radius of 4 nm which were embedded in the glass with the volume fraction of about 0.5%. We found that the figure of merit, χ(3)/ατ, where α and τ are the absorption coefficient and the response time, respectively, is also increased upon an increase of radii in the range of 1.5-4.5 nm.