Storage density of shift-multiplexed holographic memory

Abstract

The storage density of shift-multiplexed holographic memory is calculated and compared with experimentally achieved densities by use of photorefractive and write-once materials. We consider holographic selectivity as well as the recording material's dynamic range ͑M͞#͒ and required diffraction efficiencies in formulating the calculations of storage densities, thereby taking into account all major factors limiting the raw storage density achievable with shift-multiplexed holographic storage systems. We show that the M͞# is the key factor in limiting storage densities rather than the recording material's thickness for organic materials in which the scatter is relatively high. A storage density of 100 bits͞m 2 is experimentally demonstrated by use of a 1-mm-thick LiNbO 3 crystal as the recording medium.

Optimization of a thick polyvinyl alcohol-acrylamide photopolymer for data storage using a combination of angular and peristrophic holographic multiplexing

“…The aim of these new techniques is to enable the maximum number of bits͞m 2 to be stored. Anderson et al 7 has managed to store 150 bits͞m 2 and Steckman et al 8 100 bits͞m 2 . For this reason, different methods, such as angular, 4,9 -11 peristrophic, 12,13 or shift multiplexing 8,14,15 are being used to store multiple holograms at the same location.…”

Transflective multiplexing of holographic polymer dispersed liquid crystal using Si additives

“…There are a number of multiplexing schemes to store many holograms in the same volume such as angular [12][13][14][15], peristrophic [16,17], shift multiplexing [18,19] or by more than one of these techniques in combination [20][21][22], which are used to store multiple holograms at the same location. In these methods, angular multiplexing is probably the most common in which the reference beam is incident upon the sample at difference angle to record each hologram.…”

Holographic data storage: optimized scheduling using the nonlocal polymerization-driven diffusion model

“…[7][8][9] When using a photopolymer as a holographic data storage medium, one wishes to choose a recording (exposure) schedule that optimizes the total polymer generated as a direct result of the recording process and at the same time produces M gratings of maximum and ideally equal strength (refractive-index modulation size). Although work has been carried out to examine optimum scheduling experimentally and to compare multiplexing techniques, 5,[10][11][12] the material mechanisms involved and their effects on scheduling have not been clarified. The need for highly repetitive experimental procedures is due to the fact that no model has been available that satisfactorily explains the main material response characteristics of photopolymer materials.…”