SELF-FOCUSING IN PHOTOREFRACTIVE 2-WAVE MIXING

Self-focusing and self-defocusing of fight in two-wave mixing are inve stigated experimentally. Amplification and self-focusing are measured as functions of the frequency shift between signal and pump beams. A f requency dependence is found in Kramers-Kronig form, as is plausible b y the analogy of photorefractive amplification and laser amplification . Reversal of the external de field on the material or a change in the frequency shift between the signal and pump beams is found to change self-focusing to self-defocusing. (C) 1997 Optical Society of America.