We present a theoretical analysis of the influence of the collimation of a strong pump beam on a small-signal-gain line shape in a three-level Λ-type molecular system in the regime of high pump intensity when saturation and Stark (Autler-Townes) splitting of the levels of the pumping transition take place. The cases of homogeneous and Doppler-broadened pumping transitions have been considered. A significant offset, an asymmetric deformation, and a narrowing of the gain line, i.e., a spectrum focusing, have been obtained and explained as a result of the nonlinear (dispersion) and the active (gain) wave guiding of the small signal in the field of the strong pump beam.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics