Energy renormalization and binding energy of the biexciton

We deduce the energy renormalization of the biexciton resonance in ZnSe quantum wells from polarization and intensity dependent pump-probe spectroscopy in the coherent regime. We confirm that the biexciton renormalization is exactly what one would expect from a compound particle of two excitons in opposite circular polarization states. Since the biexciton binding is measured with respect to the exciton resonance one has to consider the renormalization of the latter resonance as well. We present an exact method to determine the real biexciton binding energy using the low-excitation extrapolation of the exciton-to-biexciton transition energy.