Beating structure on the spectrally resolved four-wave mixing: Polarization dependence

We have performed spectrally resolved four-wave mixing measurements on inho mogeneously broadened GaAs/AlAs quantum-well structures. Under crosslinear polarization we observed a beating structure as a function of the delay tim e at higher energy region of the emission band with period of 0.95 ps. The beating was constructive at delaytime tau = 0 ps. This behavior results fro m the interference between two biexciton intermediate states with different energies coupled to a common one-exciton state, as we show by a comparison with analytical model calculation of the double Feynman diagrams of the sa me type.