Natural fluctuations of the emission frequency of an He–Ne/CH4 3.39 μ laser

An experimental investigation was made of fluctuations in the frequency of a helium-neon laser containing a nonlinear methane absorption cell and emitting at the wavelength of 3.39 μ. Those measured were shown to be natural fluctuations. A reduction was achieved in the natural fluctuations by introducing a nonlinearly absorbing gas into the resonator cavity. The observed reduction in the spectral density of the frequency fluctuations was found to be quantitatively determined by the dynamic self-stabilization effect. It was also found that, for observation frequencies comparable with the relaxation constants of methane, an effective reduction in the spectral density took place when the radiation frequency was tuned not only close to the center of the methane transition but also within its entire Doppler absorption profile. The results of the experiments were in agreement with the conclusions of a previously performed analysis.