Spatial-mode dynamics in a photorefractive ring oscillator with induced astigmatism

We report experimental observations of the mode dynamics in a weakly multim ode photorefractive ring oscillator with induced astigmatism. First a galle ry of transverse, higher-order Gaussian modes in the system is presented. S ubsequently the dynamics of beating modes and the interactions between mode s belonging to different bases are examined. The latter show the transition of modes between the three equivalent mode families experimentally. Finall y regions of cavity symmetry leading to different spatial modes and mode dy namics are identified. (C) 2001 Optical Society of America.