Rotation spacing and multiplexing number in angle-peristrophic multiplexing holographic memory

Abstract

Holographic memory is expected to be the next-generation optical memory with several advantages including high data transfer rate and high recording density. Holographic memory enables the storage of holograms in the same location in a holographic medium typically using the angle multiplexing method. The multiplexing number is an important factor that determines the recording density when using this method. To increase the multiplexing number, it is known as an effective method to combine peristrophic (or rotation) multiplexing with angle multiplexing. We use the k-sphere to describe that the rotation spacing for peristrophic multiplexing depends on both the numerical aperture in the signal beam path and the angle between the reference and signal beams. We then formulate the rotation spacing and compare the results obtained using the theoretical formula with the measured results. Finally, we estimate the maximum multiplexing number for our experimental system using the angle-peristrophic multiplexing method on the basis of the measured results.