INTENSITY CROSSTALK AND ANGULAR SELECTIVITY OF MULTIBEAM COUPLING IN PHOTOREFRACTIVE BATIO3

Theoretical and experimental results are presented for simultaneous multibeam coupling with N signal beams and one single pump beam in photorefractive BaTiO3. The gain of each signal results from both coupling between different signal beams and coupling between each signal and the pump beam. The amount of gain that each signal receives depends on the angular configuration as well as on the incoming intensities of the interacting beams. Thus a competitive interaction of the gratings takes place, which causes some signals to receive larger intensity increments as others, dependent on the different parameters. As a result, a configuration is possible where, in contrast to conventional beam coupling, the strongest incoming signal always receives the largest intensity increment. Moreover, crosstalk between the signals can be modified by changing the incoming angles or intensities. Considering every image as the superposition of plane signal waves, it is possible to apply that competitive process to selective two-dimensional image processing, resonator configurations with selective gain or associative holographic memory systems. © 1990.