Improvement of storage density in photorefractive disk-type memory by logical multilayer recording method

Abstract

In this paper, we propose a photorefractive disk-type memory with cross polarized four-wave mixing, and suggest a method to enhance the storage density for this disk-type memory. The shift multiplexing technique, in which the feasible recording of the angularly multiplexed holograms can be implemented by means of the spherical reference beam and the rotation of the disk-shaped crystal, is applied for this memory. We analytically investigate the amounts of shift required for multiplexing differential holograms in this memory, and we carry out an experiment to verify the analytical results. Also we suggest a logical multilayer recording method as the novel scheduled recording method, and analyze the temporal property of cross polarized four-wave mixing to estimate the diffraction efficiencies from the multiplexed holograms with the method. From those analyses, it is revealed that the diffraction efficiency and the storage density of the photorefractive disk-type memory are significantly improved by this method.