Observation of photorefractive surface waves in self-defocusing LiNbO3:Fe crystal.

Photorefractive (PR) surface waves (SWs) in self-defocusing LiNbO3:Fe are studied theoretically and experimentally. We demonstrate that SWs can also be formed in a self-defocusing nonlinear medium and that the nonlocal nonlinearity (such as the diffusion component of PR nonlinearity in this Letter) is the essential cause. The forming process of PR SWs with a self-deflection course of light beams has been observed. The results indicate the possibility of concentrating light energy in self-defocusing media, taking advantage of SWs.