Photorefractive beam fanning is observed in diffusion dominated materials such as barium titanate and photovoltaic materials such as lithium niobate. Beam fanning in barium titanate has been extensively used to generate self-pumped phase conjugation. Beam fanning patterns in lithium niobate have been utilized in characterization of the photorefractive material. Two types of beam fanning have been shown to exist: deterministic beam fanning which results from the shape of the beam, and random beam fanning which originates from scattering of the incident beam from the surface and bulk of the crystal. In this paper, we report on a careful analysis of both kinds of fanning, using a focused Gaussian beam of varying waists and incorporating randomness in amplitude and phase at the surface and through the bulk of the photorefractive material. We show that in photorefractive barium titanate, deterministic beam fanning, characterized by a deflection of the main lobe of the beam in the far field and an additional sideband, may dominate over waist sizes in the tens of microns, whereas random beam fanning, characterized by multiple lobes, dominate over waist sizes larger than tens of microns.

Date Published: 24 August 2006
PDF: 8 pages
Proc. SPIE 6314, Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications XII, 631402 (24 August 2006); doi: 10.1117/12.683560

Published in SPIE Proceedings Vol. 6314:
Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications XII
Francis T. S. Yu; Ruyan Guo; Shizhuo S. Yin, Editor(s)