Analysis and applications of the speckle patterns registered in a photorefractive BTO crystal

Abstract

The features of the volume speckle pattern recording in a sillenite BTO crystal are investigated. The modulation of the speckle grains appears when the image of a random diffuser is formed onto the crystal by an optical system whose pupil consists of two identical apertures. In fact, the volume nature of the grains generates speckle overlapping regions where the modulation takes place. The 3-D modulated speckle pattern stored in the crystal leads to a space-charge field by drift of photocarriers, resulting in a refractive index modulation. By observing the diffracted read-out light is established that the index modulation in the speckle overlapping regions lead to a remarkable angular selectivity. The statistical nature behavior of the speckle distributions is considered in the theoretical analysis. A comparison between the theoretical predictions and the experimental results is done. The analysis leads to the adequate selection of the write-in parameters as it is illustrated in the optical processing applications presented.