Abstract

We propose to use a hologram as a storage medium in an all-optical feedback configuration which includes phase conjugate mirrors. The associative properties of holograms have been suggested earlier by Gabor. Addressing the system by a partial or distorted version of the stored data generates the complete version most closely associated with that input. The phase conjugate mirrors are used to form an optical resonator, containing the hologram, with threshold adjustment such that only the strongest reconstructed image and its corresponding reference beam are fully reconstructed. Because a hologram can be decomposed into a set of single holographic gratings, we demonstrate that a phase conjugate resonator can operate with multiple intracavity gratings. The resonator consisted of the phase conjugator, BaTiO₃, an intracavity hologram of two superimposed gratings, and two output couplers normal to each diffracted beam. The resonator oscillates between both output couplers unless there is a different loss in each path. By adjusting the loss and therefore the threshold, either leg of the resonator could be made to oscillate. To replace permanent holograms, the use of photorefractive materials for real-time adaptive associative memories is also presented.

© 1985 Optical Society of America