TABLE OF CONTENTS If the laser is pumped by the monochromatic radiation of another laser and the auxiliary and the operation transitions have a common upper level (Fig. 1.2) then a two-level model for the laser medium appears to be insufficient. Such a system can exhibit the effects caused by the coherent interaction between the pump field and the laser field as well as be the gain line splitting due to the Rabi oscillations in the pumping field [6, 227, 301 303].
We should differentiate between two cases that correspond to opposite limiting cases of detuning. In the first case, considered below, both the pumping and the laser field are exactly resonant with the corresponding molecular transitions. In the second case, the difference between each frequency and the corresponding transition frequency is much greater than the molecular linewidth. This second case corresponds to the Raman laser since the laser action is due to the two-photon interaction of fields with an inversionless transition between level 1 and 2. The dynamics of the Raman laser will not be considered here but it is discussed in [304 306]. In the resonance case the one-photon transitions between level 3 and 2 are of primary importance although the two-photon interactions mentioned above also contribute to the lasing and should not be ignored until the conditions for their confident suppression are provided. Essentially, we are dealing with a resonance Raman laser, but this term has not become widespread.
Mathematically, the transition from a...
