SPONTANEOUS PULSATIONS IN GAS CLASS-A LASERS WITH WEAKLY ANISOTROPIC CAVITIES

Spontaneous pulsations and polarization multistability resulting from the nonlinear interaction of two stand ing waves with an active medium in a single-longitudinal-mode Fabry-Perot gas laser with a weakly ani sotropic cavity have been studied at different cavity anisotropies and different transitions between the working levels with and without an axial magnetic field applied to the active medium. As predicted theore tically, a series of polarization dynamical phenomena have been observ ed experimentally in the He-Ne (lambda=1.15 mu m) laser in the case of orthogonal elliptically polarized eigenstates of the cavity. Periodic oscillations of two qualitatively different forms (distorted sinusoid s and large spikes), the transition between two stationary orthogonal elliptically polarized waves in the vicinity of the line center tuning which occurs through the region with polarization instability, as wel l as switches between the orthogonally polarized components when the o utput is nonstationary have been found. It is shown that the diversity of nonstationary polarization phenomena in gas lasers with weakly ani sotropic cavities is due to spontaneous pulsations of intensities, ell ipticities, and azimuths of two emitted waves, caused by the competiti on of the nonlinear active medium and empty cavity anisotropies. The r esults of the theoretical modeling are in quantitative agreement with the experimental results. [S1050-2947(97)00912-8].