Abstract

In this paper we analyze phenomenologically the excitonic nonlinearities arising from exciton-exciton interaction and phase-space filling (PSF). We make a distinction between two components of the third-order polarization: coherent and noncoherent. The first one is determined by population changes, the other is connected with a second-order contribution to the polarization. The coherent contribution to the third-order nonlinearity is explained in terms of the coherent two-photon excitation of the two-exciton states. The coherent and noncoherent components of the nonlinear polarization are demonstrated to be observable as spatially separated signals in transient degenerate four-wave-mixing.

© 1994 IEEE