Selective erasure for multiplexed holograms in photorefractive crystal using phase conjugate mirror

摘要

In this paper, we propose a selective erasure method for multiplexed holograms in a photorefractive crystal using a phase conjugate mirror (PCM). In this method, for the accurate selective erasure, we use π phase shift between the relative phase of the diffracted beam to the transmitted beam by the hologram in photorefractive crystal and the relative phase of the object beam to reference beam in recording process by setting the direction of c-axis to the appropriate direction. In the selective erasure process, the diffracted beam and the transmitted beam by the original hologram in main memory are returned to main memory by PCM. These returned beams automatically propagate through the strictly same pass as the diffracted beam and the transmitted beam. Furthermore, by these returned beams, the π-phase shifted hologram is overwritten on the original hologram by setting c-axis of main memory to the appropriate direction. Therefore, the π-phase shifted hologram is automatically overwritten on the strictly same position as the original hologram without the high precise alignment and the original hologram is selectively erased. We perform the analysis and the experiment on selective erasure and demonstrate that one of the multiplexed holograms is selectively erased with our method.