Are photorefractive ring resonators always unidirectional?

摘要

We report on the observation of bidirectional oscillations in a single photorefractive ring resonator using Ce:BaTiO_3. We show tht two oscillation beams can simultaneously be above threshold and propagate in opposite directions under different geometries. The difference in power of the two oscillation beams can reach two orders of magnitude and their stability depends on the pump beam angle of incidence and the crystal's configuration.