THEORY OF PROPAGATION EFFECTS IN TIME-RESOLVED 4-WAVE-MIXING

We study the propagation effects associated with pulsed optical four-wave mixing in a solid containing excitonic resonances. We take into account the distortion of the incident beam and the generated diffracted beam as they propagate though the sample. The possible sources of pulse distortion are different velocities and different absorption coefficients of the Fourier components involved. The result is expressed as a single integral for the case of spectral selection of the output. The theory is applied to typical resonances in semiconductors and predicts oscillatory features for thick samples. At very large sample thicknesses the theory leads to a signal for negative delay.