Cross-erasure noise in high-density holographic-storage systems

We consider a process by which images recorded in high-density holographic storage systems may be degraded. In particular, the recording of many holograms in the same volume results in cross erasure of each hologram by the sum of all the remaining holograms superposed in the same volume. This effect is, in general, spatially nonuniform and varies both transversely across each recorded image and in depth as the image propagates and diffracts throughout the volume of the recording medium. We apply a three-dimensional numerical analysis to assess the bit error rate (BER) resulting from this noise source as a function of various recording parameters. In particular, we use this analysis to determine the optimum exposure schedule for a given BER. We then describe means by which these noise sources can be largely circumvented through appropriate choice of the writing-beam intensities or the recording geometry or the use of random-phase screens.