Fundamental issues related to digital holographic data storage

Digital holographic data storage fundamentally differs from bit-wise surface recording techniques by storing the transform of a two-dimensional array of bits throughout the volume of a recording medium. Upon readout the data are transformed and detected by a 2-D detector array, providing massively parallel data streams. The third dimension of the recording medium provides an additional degree of freedom to increase capacity per unit surface area. Data storage densities exceeding those of conventional optical and magnetic recording devices by up to ten times (200 bits/cm²) have been achieved. These densities allow 200 GB of information to be stored on a single sided 5.25" disk. By reading out 2-D arrays of bits using an image capturing device, very large data transfer rates can be obtained, up to 1 Gbit/sec. In addition, acousto-optic beam steering devices are capable of addressing each of the stored pages in a few microseconds, providing phenomenally short access times to blocks of data. On the basis of the experimental results and the analysis fundamental issues are elucidated, and conclusions presented concerning the consequences for the various system architectures. Signal processing and coding approaches are discussed for over-coming some of the noise degradations. Tradeoffs between materials and systems performance characteristics are presented to achieve a competitive storage device