Zeeman effect in a ring gas laser operating well above the lasing threshold

A theoretical and experimental investigation was made of the Zeeman effect in a ring He–Ne laser, having a circularly anisotropic resonator and operating substantially above the lasing threshold. It was found that a strong-field theory must be used to explain the experimental results when the gain exceeds the losses by more than a factor of 1.3–1.4. Taking radiation trapping into account in the strong-field theory, a good quantitative description of the experimental results is obtained for all the experimental values of the gain-to-loss ratio (1.5–2.9).