KEYWORDS: Multiplexing, Holography, Holograms, Data storage, Signal to noise ratio, Diffraction, Crystals, Distortion, Signal detection, Information operations
Holograms may be superimposed in a holographic medium by a number of techniques such as angular, phase-encoded, and wavelength multiplexing. For typical architectures, crosstalk increases as the bandwidth of stored data increases. The number of superimposed holograms in an ideal medium is limited by its length L, the wavelength of light (lambda) , and index of refraction n, such that for crosstalk-limited storage we can superimpose up to 2nL/(lambda) holograms of high bandwidth. In practice, however, the properties of real materials depart from the ideal through index inhomogeneities and scattering centers, dispersion in the material response as a function of grating spatial frequency, and dispersion as a function of the wavevector and polarization of both incident and scattered light. We discuss the impact of these properties on holographic data storage and describe material, device, and system strategies designed to minimize these effects.
In this invited paper we discuss recent advances in holographic data storage using ferroelectric SBN fibers as the recording medium. An optical architecture involving an array of SBN fibers is discussed that potentially allows 2-3 orders of magnitude faster access times than for conventional magnetic data storage devices of Gbyte-size . To realize this potential we are studying the interplay between fundamental materials issues related to fiber growth and photorefractive processes underlying storage and readout processes in SBN.
KEYWORDS: Multiplexing, Holography, Optical storage, Diffraction, Volume holography, Signal to noise ratio, Data storage, Strontium, Spatial frequencies, 3D image reconstruction
The capacity of volume holographic data storage depends on the multiplexing efficiency of input holographic data arrays or pages. We compare this page-packing capacity of two common approaches: angle, and wavelength multiplexing. For maximal page packing the angular separation between the reference and signal beam incidence in the angle and wavelength multiplexing methods should be 90 degree(s) and 180 degree(s), respectively. We find that in these optimal arrangements both methods can multiplex a similar number of paraxial data-page signals, which is comparable to conceptual storage capacity limits derived from considerations of resolution in three-dimensions. In practice, the high number of multiplexed data pages predicted here will be compromised by material-related noise sources.
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