Nonlinear resonances in the natural frequency fluctuations of a two-mode He–Ne/CH4 laser

An investigation was made of nonlinear resonances in the spectral density of the natural frequency fluctuations of the intermode beats of a two-mode He–Ne laser (λ = 3.39 μm) with an internal methane absorption cell. The amplitude and width of the resonances depend on the choice of the observation frequency and, under certain conditions, it is possible to obtain resonances of width less than the homogeneous absorption line width γ^( – ).