PROPAGATION OF LASER-PULSES AND COHERENT POPULATION TRANSFER IN DISSIPATIVE 3-LEVEL SYSTEMS - AN ADIABATIC DRESSED-STATE PICTURE

The interaction of a pair of copropagating pulses with three-level Lam bda-type atoms is discussed in terms of time-dependent coupled and dec oupled superpositions \+/-] of the lower levels. Due to the explicit t ime dependence of these states there is a nonadiabatic coupling betwee n the ''bright'' state \+] and the ''dark'' state \-] in addition to t he strong coupling between \+] and the upper level \a]. We show that u nder quasiadiabatic conditions and in the presence of decay from the u pper level this coupling can be treated perturbatively and the Maxwell -Bloch equations can be solved analytically. With the help of such a p erturbation approach, coherent population transfer and formstable lase r pulse propagation are studied.