Continuum contribution to excitonic four-wave mixing

Summary form only given. We present an experimental and theoretical investigation of ultrafast transient four-wave mixing (TFWM) of GaAs-AlGaAs quantum wells for simultaneous excitation of exciton and continuum states. Recent TFWM experiments on semiconductors have shown unexpected results when both discrete exciton states and continuum states have been excited simultaneously by ultrafast laser pulses. The decay of the signal, as a function of delay, is significantly faster than the dephasing time of the excitons.