Optical associative memory using photorefractive LiNbO3:Fe hologram, and LiNbO3:Fe and BaTiO3 phase conjugate mirror

Experimental results are presented for phase conjugate (PC) wave generation, and the possibility of an application to an optical associative memory is discussed. Using an iron-doped lithium niobate single crystal, greater than 300% reflection efficiency was achieved by the degenerate four-wave mixing method, which was almost independent of the total incident optical intensity. The generator was then applied as a PC mirror to an all-optical associative holographic memory to reflect and amplify the diffracted beams. The retrieved output image was formed by using partial input illumination. Using a barium titanate single crystal, a PC reflection efficiency of about 70% was obtained by the self-pumping method. In order to accelerate the speed of the generation, a novel method called accelerated self-pumped phase conjugation (SPPC) was used. It was demonstrated that the accelerated SPPC could be directly applied to an optical associative memory to reflect the diffracted beams if a readout beam with a power of 40 μW was used