Phase Conjugate Mirrors as Thresholding Elements for Optical Associative Memories

摘要

Several ways are described to use photorefractive phase conjugators as thresholding elements for optical associative memories. The first involves background illumination of the crystal of a self-pumped phase conjugator. The second method uses a photorefractive phase conjugator designed so that its reflectivity increases with increasing signal strength. The third method uses semi-self-pumped phase conjugators in which one pump is externally provided as a thresholding reference and the other is self-induced as an oscillation beam. Two examples are the double phase conjugate mirror and a new type of phase conjugator based on injection of a counterpropagating pump beam into a undirectional ring resonator.