Stationary Transverse Field Patterns of an Optically Pumped Ring Laser

Abstract

We report experimental observations on the formation of stationary transverse patterns of the optical field in an optically pumped traveling-wave laser. The active medium of the laser is sodium dimer (Na2) vapor. The field patterns arise from the superposition of phase-locked higher-order transverse optical modes of the laser resonator. The astigmatically compensated ring resonator of the laser has the transverse-mode structure of a cylindrically symmetric, semi-confocal cavity. The narrow gain linewidth of the active medium permits to selectively excite groups of frequency-degenerate transverse resonator modes of common order. The shapes of the emitted field patterns are in agreement with the predictions of Brambilla et. al. (1990 NDOS conference, Afton, Oklahoma, paper ThB3).