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

We demonstrate recording of the gradient-type correlation filter for a spec kle pattern in Bi12SiO20 (BSO) single-crystal fibers grown by the laser-hea ted pedestal-growth (LHPG) method. The filter linearly transforms small lat eral displacements of the speckle pattern into the modulation of intensity transmitted through the photorefractive fiber. Despite the fibers possess h igh concentration of inhomogeneities, the intensity modulation depth reache s 25% that is comparable with values obtained with a high-optical-quality s amples cut from a bulk crystal. (C) 2000 Elsevier Science B.V. All rights r eserved.