Abstract

In time-resolved four-wave mixing (FWM) experiments, two ultrashort pulses delayed by Δt and with wavevectors k₁ and k₂ interfere in a sample to produce a diffracted signal (DS) in the direction k_s = 2 k₂ − k₁. In the case of a homogeneously broadened system, the DS is emitted immediately after the second pulse corresponding to the "free- induction decay" of the nonlinear polarization. Because of the short dephasing times T₂ in solids, the DS is usually not time-resolved, but is measured as a function of Δt using a slow detector. Valuable information contained in the temporal profile of the DS is thus lost Here, we report the first measurement of the temporal evolution of the DS on a fs time scale for the case of selective excitation of semiconductors.

© 1992 The Author(s)