A nonlinear spectroscopic technique using a ring laser

A description is given of an experimental method of determining the ratio of the nonlinear interaction and self-interaction parameters of the opposite waves in the active medium of a ring laser. The method involves analyzing the modulation components of the opposite wave intensities for the case of asymmetric coupling. An experiment using an He–Ne ring laser emitting at λ = 0.63 μ gave the dependence of the ratio of the nonlinear parameters on the pressure of the He–Ne mixture. By analyzing the experimental data on the basis of the existing theory of nonlinear polarizability and allowing for resonance radiation trapping, it was possible to determine the trapping parameter and the pressure derivative of the relaxation constant of the lasing transition. An analysis was made of the possible influence of elastic collisions on the results.