Abstract

Presently, time-resolved four-wave mixing is a powerful tool for studying ultrafast relaxation processes of optically exited states in condensed matter.^[1] This technique was applied to make measurements of relaxation times in bulk Si at the room temperature. The excitation pulses with durations t_p much longer than the relaxation times were used. It follows from our recent simulations of this regime that the maximum of the correlation trace is detuned from the zero delay between the pulses and contains information about (i) the dephasing time T₂ (if T₂ and T₁ are of the same order), (ii) the population relaxation time T₁ (if T₁ is longer than T₁). Moreover, in this case (t_p ≫T₂, T₁) the shape of the curve is determined by the pulse autocorrelation function.

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