Spontaneous Self-Trapping of Optical Beams in Metastable Paraelectric Crystals

We report on the observation of a new mechanism for self-trapping of optical beams: self-trapping that stems from spontaneous creation of ferroelectric crystalline clusters, seeded by a weak photorefractive diffusion field. This is an evident observation of the highly nonlinear aspects of propagation in a thermodynamically metastable system, including optically driven crystalline ordering in a medium undergoing a phase transition.