Self-focusing by thermal heating because of absorption of a guided light beam in a planar strontium-barium-niobate waveguide is of interest for all-optical data processing. When a guided probe beam intersects the pump beam under a small angle inside the waveguide, the self-focusing effect in conjunction with self-bending because of the photorefractive effect can be used for large angle deflection of the probe beam and for switching with time constants of fractions of milliseconds. Deflection angles of the outcoupled probe light up to 0.23rad in air and frequencies up to 3kHz for optical switching are reached in the experiment. © 1998 American Institute of Physics.