Polarization choices in exciton-biexciton system of GaAs quantum wells

We study the induced absorption due to biexciton formation in absorption bleaching pump-probe signals and the quantum beats between exciton and biexciton in the four-wave-mixing signals. The origin is confirmed by the polarization dependence of the signals in both experiments. The definite discrimination between exciton-biexciton quantum beats and the others by the polarization choices is demonstrated clearly. We also show the well-width dependence of the biexciton binding energy that is determined by the period of the quantum beats in the range of well width 45--150 {} of GaAs/Alₓ{Ga}_{1{{-}}x}$As (x=0.3--1.0) multiple quantum wells.