The preparation and optical characteristics of single crystals containg FA centers (KCl doped with 3mol% NaCl or LiCl), and their applications to optical memory are presented. By the diffusion annealing after sufficient additive coloration, F centers can be distributed uniformly in the crystals (about 35×35×1-10mm3). The crystals containing FA centers produced by optical bleaching can be used as the three dimensional recording medium. The optical information is recorded by aligning the anisotrpic FA centers with the plane polarized He-Ne laser light. The negative and positive images are produced by a single recording. The resolution is higher than 2500 1/mm. The optical sensitivity is about 5 mJ/cmcm2. The ability of three dimensional recording is utilized for several types of volume holograms.
