SIZE-DEPENDENT ENHANCEMENT OF 3RD-ORDER OPTICAL NONLINEARITY IN CUBRXCL1-X NANOCRYSTALS EMBEDDED IN GLASS

We have studied the size-dependence of the third-order optical nonline arity in CuBrxCl1-x (x = 0.26 +/- 0.01) nanocrystals with radii rangin g from 5.3 -11.5 nm by means of degenerate four-wave mixing, time reso lved luminescence and resonant luminescence experiments. The absolute value of third-order susceptibility chi((3)) exhibits resonant behavio r at the confined exciton level, and the resonant chi((3)) increases w ith increasing crystallite radius R. Assuming a two-level atomic model , we have analyzed the size-dependence of chi((3)) and obtained the R- 2.1-dependence of the oscillator strength of confined excitons. The fi gure of merit increases from 0.65 to 3.4 esu.cm/s with increasing size .