We describe analytically and numerically the process of population transfer by stimulated Raman adiabatic passage through a bright state when the pulses propagate in a medium. Limitations of the adiabaticity are analyzed and interpreted in terms of reshaping of the pulses. We find parameters for the pulses for which the population transfer is nearly complete over long distances.

Propagation of a pulse pair in a nondissipative three-level medium is investigated in the adiabatic-following approximation to a trapped state. The general case of unequal oscillator strengths of two electric dipole transitions in an atom is studied analytically, and the adiabaticity criterion for the matter-field interaction is derived. It is shown that the interaction adiabaticity strongly depends on the relationship between oscillator strengths. A simple expression specifying the critical propagation length at which the stimulated Raman adiabatic passage process is still effective is derived. An estimate of the propagation distance at which a complete energy transfer from the pump pulse into the Stokes pulse occurs is made.

We present extended experimental investigations and numerical studies on coherently driven population inversion in a three-state molecular quantum system by sequential double-Stark-chirped rapid adiabatic passage ͑SCRAP͒ ͑D-SCRAP͒ and three-state-SCRAP ͑T-SCRAP͒. D-SCRAP and T-SCRAP are alternative extensions of SCRAP. In D-SCRAP and T-SCRAP, a ⌳-type quantum system is coherently driven by two laser pulses, the pump and Stokes pulses, which are slightly detuned from transition frequencies. A third strong laser pulse induces dynamic Stark shifts of the relevant transitions. If the timing of the three pulses is appropriately chosen, the quantum system is prepared to almost complete population inversion between the two lower states in the ⌳-type level scheme. The transfer process is robust with regard to fluctuations of experimental parameters, provided some limitations are met. The paper presents convincing experimental data on D-SCRAP and T-SCRAP, driving efficient and selective population transfer to a highly excited vibrational level in nitrous oxide ͑NO͒ molecules. T-SCRAP yields transfer efficiencies of up to 95%. The efficiency of T-SCRAP is almost uneffected by the limited lifetime of the intermediate state in the ⌳ system. The paper also presents data on the accurate experimental determination of Rabi frequencies and Stark shifts. This involves measurements of power broadening, Autler-Townes splittings, and Stark-shifted spectral lines in NO molecules. Moreover, we discuss the calibration of absolute transfer efficiences by comparison with stimulated emission pumping. The experimental data are confirmed by extended numerical simulations. The simulations also serve to intensively study the properties and dynamics of D-SCRAP and T-SCRAP.

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