Stable self-focused beams in a photorefractive Bi12TiO20 crystal

We present experimental results on the self-focusing of light beams in a photorefractive, optically active Bi12TiO20 crystal. Using circular polarization of the input HeNe laser beam we succeeded to create a stable self-focused, asymmetric light-beam over several hours. Depending on external parameters, like the external electric field and the intensity ratio, a transient symmetric state is observed.