FILTERING EFFECTS OF SPATIALLY MODULATED BEAMS IN PHOTOREFRACTIVE OSCILLATORS.

Summary form only given, as follows. The authors discuss the properties of various photorefractive oscillators with nonuniform (image hearing) pump beams and explain the lack of spatial information crosstalk between the interacting waves, which is in contrast to the case of externally pumped four-wave mixing. A detailed theoretical and experimental study was carried out with ring and double-phase-conjugate mirrors as well as with two-beam coupling configurations. These filtering properties were used for beam cleanup, bidirectional light modulation, and other optical processing applications such as pictorial edge enhancement and thresholding.