Theoretical and experimental results are presented for simultaneous multibeam coupling in photorefractive BaTiO3. Within a single crystal, multiple signals are amplified through a coupling processs that employs a single pump beam. The amplification of each signal results from both coupling between signal and pump beam and coupling between different signals. The amount of gain that each signal receives is dependent on the angle relative to the c-axis of the crystal and on the intensities of the incident beams. Thus a competitive interaction for the amplification of the signals takes place: For a specific range of coupling coefficients and intensities the strongest incident signal receives the largest energy increments. In a resonator that employs photorefractive gain such a process can be used to keep the strongest beam oscillating and to suppress weaker ones. Thus it is possible to apply that competitive process to an associative holographic memory.
"Multibeam Coupling In Photorefractive BaTiO3", Proc. SPIE 1127, Nonlinear Optical Materials II, (22 December 1989); doi: 10.1117/12.961427; https://doi.org/10.1117/12.961427