Nondegenerate four-wave mixing is analyzed with respect to biexcitonic contributions in the third-order nonlinear susceptibility x(3) . The presence of biexcitons causes a distinct asymmetry in the frequency dependence of self-diffraction. By measurement of the dependence of the intensity of the self-diffracted signal on detuning between the two incident laser beams, the biexciton binding energy is determined to be EXX=7.8 meV for cadmium sulfur quantum dots of R=7.5 nm embedded in glass. Thus, even for weakly confined II–VI quantum dots with R~2.7aB , a confinement-induced enhancement of EXX was found.
© 1998 Optical Society of america
(190.0190) Nonlinear optics : Nonlinear optics
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(190.4720) Nonlinear optics : Optical nonlinearities of condensed matter
(300.6270) Spectroscopy : Spectroscopy, far infrared
(300.6470) Spectroscopy : Spectroscopy, semiconductors
H. Spöcker, M. Portuné, and U. Woggon, "Biexcitonic fingerprint in the nondegenerate four-wave-mixing signal of weakly confined cadmium sulfur quantum dots," Opt. Lett. 23, 427-429 (1998)