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A number of spatially nonlinear-optical materials, such as photorefractive media, are suitable for volume holography. High Bragg selectivity of thick media has led to the development of applications of multiplex volume holography ranging from binary and analog data storage, to associative memory, to neural networks, to optical interconnects. An important consideration is the balance between capacity and noise. We examine here crosstalk for angular, phase-encoded, and wavelength multiplexing for holographic data storage and describe the properties of null-matched arrangement of reference waves, presenting new results for adjacent, sparse, and fractal strategies. We emphasize the impact of signal bandwidth on crosstalk and describe how crosstalk limits storage capacity. We consider first crosstalk due to Bragg mismatch (mismatch-limited crosstalk), and then relate it to other noise sources present in a holographic memory system. >

Certain memory applications based on photorefractive media require the ability to conveniently fix holograms. An attractive alternative is to sufficiently prolong the readout time. Low photoexcitation at long wavelength augmented by self-diffraction can increase readout time by a few orders of magnitude. The interaction of the writing and readout waves, both of the same wavelength, with the photorefractive space charge field has been investigated theoretically and experimentally. Dynamics of beam coupling and self diffraction, in certain geometries, can lead to an initial increase followed by non-exponential decay of the diffracted signal during readout. Here we study how the difference in gain, lifetime, photoexcitation and absorption at different wavelengths - which require changing incident angles to satisfy the Bragg condition - affect the decay dynamics of photorefractive gratings. >