PHOTOREFRACTIVE RING OSCILLATORS

We consider the theory of photorefractive ring oscillators, using our unified solution method. Both unidirectional and bidirectional ring re sonators are analyzed, based on the two-wave mixing process with cross ed polarization and the four-wave mixing process with parallel polariz ation in photorefractive crystals. We high-light symmetries between th e transmission and the reflection geometries of these processes and us e them to write analytical expressions for oscillation conditions in a ll the cases. Symmetry breaking is noted in the four-wave mixing betwe en the transmission and the reflection grating cases. An optical trans istor based on photorefractive rings is proposed.