Photorefractive beam fanning
Photorefractive beam fanning a photorefractive phenomenon in which a beam of coherent light is scattered into a fanned pattern by a photorefractive crystal (e.G., Barium titanate, lithium niobate). When a laser beam passes through a photorefractive crystal, significant scattering often occurs. The scattered light appears to be asymmetrical with respect to the beam except for propagation along the c-axis. For laser beams of moderate power, the scattered light appears to develop slowly in time and eventually reaches a steady-state scattering pattern. This is known as photorefractive beam fanning. The beam fanning originates from an initial scattering due to crystal imperfections. The initially scattered light is amplified due to the physical overlap and the energy coupling between the incident beam and the scattered beam. Beam fanning often occurs in highly efficient photorefractive media, even if the material is near-perfect. Photorefractive beam fanning plays an important role in the initiation of many phase conjugators and resonators, even through the fanning itself can be a source of noise in many experimental measurements.
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Author of the text: Ed. P.A. Laplante Boca Raton: CRC Press LLC, 2000
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