Propagation of complex laser pulses in optically dense media

Ultrafast laser pulses with complex envelopes (amplitude and frequency modu lated) an used to excite an optically dense column of rubidium vapor. Pulse reshaping, stimulated emission dynamics, and residual electronic excitatio n in the Rb vapor are all shown to depend strongly on the laser pulse shape . Pulses that produce adiabatic passage in the optically thin limit exhibit more complex behavior in optically thick samples, including an unexpected dependence on the sign of the frequency sweep. Numerical solutions of the M axwell-Bloch equations are shown to account for our results.