Stabilization of the frequency of a two-mode He–Ne laser with the aid of magnetic hyperfine structure components of the λ =3.39 μ line of methane

The frequency of a two-mode He–Ne laser (λ =3.39 μ) with an intracavity telescopic beam expander was stabilized for the first time using resolved magnetic hyperfine structure components of the methane F⁽²⁾₂ line, selected by the highly sensitive method of frequency detection of saturated dispersion resonances. Investigations were made of the stability and shifts of the laser frequency as functions of various physical parameters. Operating conditions were found for minimizing the shifts in the stabilized frequency over a wide range of parameter variations. The long-term frequency stability of the radiation emitted by a compact twomode laser with a telescope was found to be 2×10^–14 for a 100-sec averaging time, while the shifts in the stabilized frequency did not exceed a few hertz over a wide range of variation of the main parameters.