SPATIAL-FREQUENCY RESPONSE OF PHOTOREFRACTIVE PHASE CONJUGATORS WITH CE-BATIO3

We propose and demonstrate an interferometric method to measure the sp atial-frequency response of photorefractive phase conjugators with Ce: BaTiO3. Two coherent beams are incident on a crystal and form an inter ference pattern inside the crystal. The two beams undergo stimulated p hotorefractive backscattering, which creates their corresponding phase conjugations. Then the four waves interact within the crystal. The sp atial-frequency resolution of the phase conjugators is measured to be as high as 3750 Line pairs/mm by use of the interferometric method. Th ere are several factors that limit the measured spatial resolution whe n using a U.S. Air Force Resolution Chart. The output modulation devia tes from the input modulation for high spatial frequencies. In the pre sence of a strong additional pump beam, the output modulation of the p hase conjugators is almost the same as the input modulation for a wide range of input spatial frequencies. The phase conjugator exhibits a l arge dynamic range of intensity. We analyze theoretically the modulati on transfer function of photorefractive phase conjugators with Ce:BaTi O3 for two mutually coherent beams. The theoretical analysis is in agr eement with the experimental results within a small incident-angle reg ion. (C) 1998 Optical Society of America.