Biexcitonic contribution to the degenerate-four-wave-mixing signal from a GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum well

We report experiments on degenerate four-wave mixing in a high-quality GaAs/${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As quantum well using the time-resolved self-diffraction technique. Frequency-dependent measurements around the heavy-hole exciton transition reveal a strong biexcitonic nonlinearity.