The polarization properties of ring resonators for the case of a single discharge tube with Brewster angle windows in the optical circuit are investigated. The azimuths of polarization of the traveling waves and the related reflection losses due to the Brewster angle windows are calculated as a function of the orientation angle of the Brewster angle windows for different anisotropic reflectances of the reflecting mirrors of the resonators. The experiments are made on a triangular ring laser which is operated at the 6328 Å He-Ne line. The measured polarization and intensity of the output light agree very well with the theoretical predictions.
T. Yoshino and T. Sumimoto, "Polarization Properties of a Triangular Ring Laser Having a Discharge Tube with Brewster Angle Windows," Appl. Opt. 9, 1831-1833 (1970)