Numerical simulation of the quasi-resonance transient double resonance regime in a scheme with the common upper level for a small inhomogeneous broadening of quantum transition lines

The transient double resonance in the Λ-scheme is numerically investigated for short input laser pulses whose spectral widths exceed noticeably the Doppler width of quantum transitions. The case of the exact resonance is considered, when the frequencies of input pulses coincide with the central frequencies of quantum transitions, and the quasi-resonance case, when this coincidence is slightly violated. It is shown that a pulse with a lower frequency is shortened and considerably amplified during its propagation in a medium. A pulse with a higher frequency transforms to a pulse with a ridge envelope, which virtually does not decay during its propagation despite the presence of irreversible relaxation. Estimates were performed for quantum transitions in the ²⁰⁸Pb atom.