24 August 2006 Distinction between deterministic and random beam fanning in photorefractive materials
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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.
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Partha P. Banerjee, Partha P. Banerjee, Arun M. Venkataraman, Arun M. Venkataraman, } "Distinction between deterministic and random beam fanning in photorefractive materials", Proc. SPIE 6314, Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications XII, 631402 (24 August 2006); doi: 10.1117/12.683560; https://doi.org/10.1117/12.683560

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