Propagation and amplitude correlation of pairs of intense pulses interacting with a double-Λ system

The propagation of intense laser pulses through a four-level atomic system in a double-{Λ} scheme is examined. Under conditions of adiabatic perturbation of the atomic quantum state, paired pulses with arbitrary shapes establish a correlation between their amplitudes and reach a quasiform-stable regime of propagation. The amplitude correlation is a feature of pulse matching, while the propagation presents the same properties as the so-called adiabatons, predicted and observed in single-{Λ} systems. We show that in the double-{Λ} scheme the phenomena of pulse matching and adiabaton-type propagation are associated with two distinct propagation normal modes. {} 1996 The American Physical Society.