Propagation of high-intensity short resonant pulses in inhomogeneously broadened media

We investigate the areas of extremely short, intense (area greater than or equal to pi) resonant optical pulses on propagation through an inhomogeneously broadened atomic medium. Experimentally, there is no apparent change in the shape of such pulses on propagation, in contradiction to the area theorem. Here we show that, although the main part of the pulse is unchanged for short propagation distances (alpha l similar to 1), it is followed by a long weak tail formed by free induction decay from the excited atoms. The tail lengthens and oscillates on propagation through the medium and permits the area theorem to be obeyed. These oscillations, which depend critically on the Doppler broadening, are reflected in the spectral analysis of the propagated pulse. We also introduce another mechanism for pulse reshaping, which is a generalization of the McCall-Hahn pulse breakup and operates at long propagation lengths (alpha l much greater than 1), where the number of absorbing atoms encountered by the pulse is comparable with the number of photons in the pulse. (C) 1999 Optical Society of America [S0740-3224(99)01207-2].