Photorefractive fibers for adaptive correlation filtering of a speckle-pattern displacement

We demonstrate recording of the gradient-type correlation filter for a speckle pattern in Bi12SiO20 (BSO) single-crystal fibers grown by the laser-heated pedestal-growth (LHPG) method. The filter linearly transforms small lateral displacements of the speckle pattern into the modulation of intensity transmitted through the photorefractive fiber. Despite the fibers possess high concentration of inhomogeneities, the intensity modulation depth reaches 25% that is comparable with values obtained with a high-optical-quality samples cut from a bulk crystal.