Investigation of changes in the angular divergence of helium-neon laser radiation (λ = 3.39μ ) as a function of the dispersion characteristic of the active medium

The angular divergence of helium-neon laser radiation was found to depend on variation of the emission frequency within the limits of the gain profile of the active medium. The maximum relative change in the angular divergence was 4 ± 2%. This change appeared because of a nonlinear frequency dependence of the refractive index of the active medium in the region of the Doppler-broadened gain profile. The effect appeared particularly clear in the case of long optical paths.