Quantum interference and slow light propagation in cold samples of open three-level atoms

We investigate theoretically the propagation of a probe laser pulse through a cold sample of three-level atoms in the presence of a strong coupling field. Our numerical analysis shows that the electromagnetically induced transparency phenomenon produces very small group velocities for the probe pulse even if the three-level atomic system is open, i.e. in the presence of decay channels to levels not excited by the laser radiation. The role of the atomic momentum on the slow light propagation is briefly discussed.