Coherence creation in an optically thick medium by matched propagation of a chirped laser pulse pair

摘要

We consider the simultaneous propagation of a pair of Raman-resonant,frequency-modulated (chirped) laser pulses in an optically thick medium,modeled by an ensemble of $\Lambda$-atoms. A self-organization ('matching`)effect is shown for the chirped pulse pair, which leads to a quasi-losslesspropagation. Furthermore, we demonstrate that a well-defined coherentsuperposition of the atomic ground states and, correspondingly, a coherence isrobustly created in the medium that can be controlled by amplitudes of thelaser pulses. The proposed scheme can be applied to substantially increase theefficiency of the optical wave mixing processes, as well as in other nonlinearprocesses where the initial preparation of a spatially extended medium in acoherent superposition state is required.