BIEXCITONIC FINGERPRINT IN THE NONDEGENERATE 4-WAVE-MIXING SIGNAL OF WEAKLY CONFINED CADMIUM SULFUR QUANTUM DOTS

Nondegenerate four-wave mixing is analyzed with respect to biexcitonic contributions in the third-order nonlinear susceptibility chi((3)). T he presence of biexcitons causes a distinct asymmetry in the frequency dependence of self-diffraction. By measurement of the dependence of t he intensity of the self-diffracted signal on detuning between the two incident laser beams, the biexciton binding energy is determined to b e E-xx = 7.8 meV for cadmium sulfur quantum dots of R = 7.5 nm embedde d in glass. Thus, even for weakly confined II-VI quantum dots with R s imilar to 2.7 alpha(beta), a confinement-induced enhancement of E-xx w as found. (C) 1998 Optical Society of America.