DYNAMICAL STRUCTURES OF A PHOTOREFRACTIVE OSCILLATOR

Using a photorefractive oscillator (PRO) with a stable resonator, we i nvestigate patterns produced from the transverse mode families of orde r 0-3. The phenomena observed include vortices which move along circul ar or spiral trajectories and vortices which periodically change the s ign of their topological charge. In addition, we observe behavior whic h is unlike that expected for lasers, despite the established analogy between the laser and the PRO. This includes pulsing of mode patterns which are otherwise expected to be stable, and also stable rotation of Gauss-Laguerre mode patterns. These effects indicate a much stronger self-focusing in the PRO than in lasers.