Off-resonance dispersion profile effect in gas laser resonators

Diffraction losses and resonant frequencies of a gas laser resonator perturbed by an off-resonance dispersion profile, due to nonuniform radial distribution of excited atoms, are predicted by extending the ray transfer matrix formalism. These predictions are tested experimentally by using the laser beam as a probe. Experiments are done with a 6401-A He-Ne laser. In this case perturbations are induced by the strong neon absorption line at 6402 A. The two studied properties lead to determinations of the population of neon 1S5 metastable level which are both in good agreement, so the validity of the theoretical analysis presented is confirmed. It is also shown that off-resonance dispersion profile effects occur in the 6328-A He-Ne laser.