Spectroscopic investigations of power resonances in a ring He–Ne/CH4 laser

Detailed experimental measurements were made of the parameters of narrow power resonances in an He–Ne ring laser (λ=3.39μ) with a methane absorption cell. These parameters were determined as a function of the pressures in the active and passive media, and also as a function of the degree and phase of the coupling between the opposite waves via scattering. The conditions were found for stable narrow resonances of a Lorentzian profile located at the center of the absorption line. The ring laser frequency was stabilized and the frequency shifts of the power resonances, governing the reproducibility of the He–Ne/CH₄ ring laser frequency, were investigated.