Crosstalk noise, due to the finite dimension of the recording medium, is a fundamental limitation to storage capacity in volume holographic memory. We present a general theoretical analysis on the crosstalk noise in angle- and wavelength-multiplexed volume holographic memory systems. Results on storage capacity and its dependence on hologram separation and required signal-to-noise ratio are obtained and discussed. Crosstalk noise may also arise from the expansion or shrinkage of the storage medium during and after the hologram recording process. Its effects, including Bragg mismatch, pixel displacement and impulse broadening, are analyzed for Fourier-plane holographic memories. Complete compensation and optimization to eliminate or reduce these effects are presented and discussed.

The author presents a tutorial review of various kinds of optical phase conjugators using photorefractive materials. These include externally pumped phase conjugators (EPPCs), self-pumped phase conjugators (SPPCs), and mutually pumped phase conjugators (MPPCs). He briefly describes optical phase conjugation and the photorefractive effect. He also describes wave mixing in photorefractive media. The energy transfer in two-wave mixing and the holographic nature of four-wave mixing are discussed.>