Size dependence of optical nonlinearity of CdSSe microcrystallites doped in glass

Abstract

This paper investigates the size dependence of the effective nonlinear cross section σeff and the carrier recombination time on the size of CdS0.12Se0.88 microcrystallites with average radii of 10, 30, 50, and 100 Å 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-Å microcrystallites. The diffraction efficiency of DFWM is almost the same for all microcrystallites, that is, σeff has a weak size dependence. Smaller microcrystallites show smaller magnitudes of the third-order nonlinear susceptibility ‖χ(3)‖, which is calculated from the measured effective nonlinear cross section and the carrier recombination time.