SPATIOTEMPORAL INSTABILITIES IN A FABRY-PEROT RESONATOR FILLED WITH SODIUM VAPOR

We report on instabilities in the transmitted polarization of a laser beam crossing a planar Fabry-Perot resonator filled with sodium vapor, at a null magnetic field, when the input field is linearly polarized and tuned near the center of the Dl line. We have measured bifurcation diagrams in the input-power-cavity-detuning parameter space at variou s angles of incidence. The system shows monostability, bistability, an d limit cycles in the transmitted polarization. Oscillations appear on ly when the angle of incidence is different from zero and the oscillat ion phase changes with the position on the transverse profile. The obs erved dynamics is explained by a simplified model which accounts for Z eeman and hyperfine pumpings, focusing and defocusing effects, and ato mic motion. By means of this model, we have determined the codimension ality of the system within a theory of the dynamical systems.