Abstract

We report the observation of low-frequency (1–100-kHz) intensity oscillations in the output of a polarization isotropic He–Ne laser operating at 3.39 μm. Oscillations have been observed in the total intensity as well as in the intensity of orthogonally polarized (linear or circular) components of the emitted light. While the intensities of either pair of orthogonally polarized components oscillate with strictly opposite phases, the pulsations in the total intensity are not in phase with those of any polarization, suggesting that the laser output in the unstable regime does not have a definite state of polarization. Adjusting the values of the control parameters (detuning, excitation, ratio between the cavity losses for the two polarization components) we observe stable single-polarization output, nearly sinusoidal oscillations, and spiky pulsations. The results agree qualitatively with recent theoretical predictions¹ for the time-dependent behavior of polarization isotropic lasers.

© 1988 Optical Society of America