QUANTUM SIZE EFFECTS AND OPTICAL NONLINEARITY OF CONFINED EXCITONS IN SEMICONDUCTING MICROCRYSTALLITES

We report linear and nonlinear optical response of CdSe and CuCl microcrystallites embedded in glasses. In CdSe microcrystallites, we observe both the individual confinement of the electron-hole pair for R < 68 angstrom and the exciton confinement for R > 120 angstrom. Furthermore, we have investigated the size-dependent enhancement of the third-order nonlinear susceptibility chi(3) in CuCl microcrystallites with radii of 15 to 80 angstrom. The absolute values of chi(3) measured at 80 K is increased as a function of the radius and subsequently decreased after reaching a maximum value at approximately 55 angstrom. These results clearly confirm the mesoscopic enhancement of the nonlinear optical response of the quantum confined exciton system.