SIZE DEPENDENCE OF OPTICAL NONLINEARITY OF CDSSE MICROCRYSTALLITES DOPED IN GLASS

This paper investigates the size dependence of the effective nonlinear cross section sigma(eff) and the carrier recombination time on the size of CdS0.12Se0.88 microcrystallites with average radii of 10, 30, 50, and 100 angstrom by degenerate four-wave mixing (DFWM) experiments. The decay curves of the DFWM signal as a function of the probe delay time have fast and slow components. As the microcrystallite size decreases, the fast component becomes dominant and a carrier recombination time of 2 ps was observed in the 10-angstrom microcrystallites. The diffraction efficiency of DFWM is almost the same for all microcrystallites, that is, sigma(eff) has a weak size dependence. Smaller microcrystallites show smaller magnitudes of the third-order nonlinear susceptibility \chi(3)\, which is calculated from the measured effective nonlinear cross section and the carrier recombination time.