Emission of a molecular gas HCl laser at 4 μm upon optical pumping by a tunable colour centre laser into the third vibrational overtone

The parameters of an HCl gas laser optically excited into the third vibrational overtone are studied. The laser was excited by a single-frequency tunable F₂^-:LiF colour centre laser. Upon pumping the HCl gas into the (3–0) R(3) transition at 1.189 μm, lasing was observed at the (3–2) P(5) (1.189 μm) and (2–1) P(6) (3.769 μm) transitions, respectively. The experimental slope efficiency of the molecular laser achieved 2%.