Role of exciton-exciton interaction on resonant third-order nonlinear optical responses

Weakly interacting boson model with the account for the bound biexciton is employed to obtain the evolution equations for the macroscopic exciton polarization. The polarization-sensitive degenerate four-wave mixing measurements in frequency domain enable us to estimate the relative contribution of the bound biexciton state on the nonlinear optical response. In the time-domain measurements, we study the amplitude and phase of the beating in the time-integrated four-wave mixing signal. On the basis of the developed evolution equations, we show that the phase shift of the beating signal is polarization sensitive and is determined by the interplay between excitation-induced dephasing, exciton-exciton interaction and other mechanisms of the nonlinearity.