Circling vortices and pattern dynamics in a unidirectional photorefractive ring oscillator

摘要

We report results on unidirectional oscillation in a photorefractive oscillator implemented with BaTiO_3 that is actively stabilized. Dynamic spatial patterns and pattern competition were observed, depending strongly on the Fresnel number of the system. As the origin for spontaneous pattern alternation we identified variations in the cavity length that are in turn mainly due to temperature fluctuations. By varying the cavity length, we were able to adjust stable patterns of different mode families and control pattern dynamics as mode beats, optical vortices and their rotations and more complex pattern dynamics for higher Fresnel numbers.