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

We study the propagation effects associated with pulsed optical four-w ave mixing in a solid containing excitonic resonances. We take into ac count the distortion of the incident beam and the generated diffracted beam as they propagate though the sample. The possible sources of pul se distortion are different velocities and different absorption coeffi cients of the Fourier components involved. The result is expressed as a single integral for the case of spectral selection of the output. Th e theory is applied to typical resonances in semiconductors and predic ts oscillatory features for thick samples. At very large sample thickn esses the theory leads to a signal for negative delay.