Differences in polarization dynamics of the electromagnetic field in xenon and neon lasers

We have experimentally observed the appearance of oscillations in the state of polarization of a constant-total-intensity, quasi-isotropic, HeXe, single-"geometrical"-mode laser operating at ? = 3.51 ?m. Similar oscillations, accompanied by oscillations in the total intensity, have been detected also in a HeNe laser operating at ? = 3.3922 ?m under the same experimental conditions. While the oscillations in the HeXe laser are understandable in terms of competition between the field amplitudes of two modes of different polarization, those in the HeNe may involve the atomic dynamics as well. © 1989.