Frequency reproducibility of ring He–Ne/CH4 lasers

An investigation was made of the factors governing the frequency reproducibility of ring gas lasers stabilized using resonances of nonlinear absorption in methane. The laser was of monolithic construction convenient in many practical applications. Frequency stabilization by competitive and phase resonances of nonlinear absorption ensured a frequency reproducibility of 5×10^–13 and 4×10^–12, respectively, and this reproducibility was governed mainly by the inaccuracy of the establishment of the necessary pressure in the amplifying medium. A theory of nonlinear resonances in ring gas lasers was developed for an arbitrary degree of saturation of the absorption and this theory could be compared directly with the experimental results.