Theory of coherent transients in semiconductor pump–probe spectroscopy

Probe-transmission spectra are calculated for a semiconductor that is excited by ultrashort pulses well above its band edge. Coherent coupling of the light field to the band-to-band transitions is assumed, neglecting the mixing of different momentum states. The transmission spectra exhibit pronounced oscillatory structures caused by the interaction of the probe pulse with the medium polarization, which is driven by the pump pulse. The details of the oscillations are determined by the temporal separation between pump and probe pulses and by the total temporal width of the pump pulse. Characteristic modifications of the spectra are obtained for strong pump fields (π and 2π pulses). Possible applications of the theoretical results for the determination of intraband scattering times in semiconductors are discussed.