Coherent population transfer in three-level Lambda systems by chirped laser pulses: Minimization of the intermediate-level population

Adiabatic passage induced by chirped laser pulses in three-level Lambda sys tems is investigated. Two different strategies for efficient population tra nsfer (equal and opposite sign of the chirp) are analyzed. The role of detu ning, crucial for the attempt to reduce the population of the intermediate state, is demonstrated. The scheme of adiabatic passage by laser pulses wit h chirps of different sign is not symmetric with respect to the sign of the one-photon detuning. Blue detuning results in a smaller transient populati on of the intermediate state than does red detuning. The results are explai ned on the basis of dressed states. Numerical results for a fully off-reson ant adiabatic passage scheme, based on two pulses with the same sign of the chirps, are also considered. The robustness of the schemes in terms of the Rabi frequency, chirp rate, detuning, and time delay of the pulses is expl ored. [S1050-2947(99)00606-X].