Holographic Data Storage (Score 5)

Litium Niobate is one cystalline candidate for holographic data storage. However, it is too expensive to compete with more conventional types of data storage.

There's ongoing research ( http://nanonet.rice.edu/research/boy d_res.html) to use photopolymers as a cheaper holographic medium. If such research comes to fruition, you're more likely to see CD like disks coated w/ a holographic layer than the typical science fiction "data crystal."

Other problems w/ holograms:
- materials are not totally transparent, so "cubes" might be out of the question

-materials must be chemically resistant to the atmosphere (e.g. oxidation, humidity), which might necessitate that they are coated. Such a coating might have deleterious effects on the substrates optical properties.

- storing a hologram changes the structure of the crystal, which can cause limits of data density and beam penetration.

- multiple holograms can be stored at the same location by rotating the crystal, but each hologram attenuates the possible intensity of subsequent holograms in that location.

- holographic "efficency" is a funciton of the difference between the refractive indices of the substrate components. photopolymers have a very small range of refractive indices as oppossed to inorganic crystals.

Overall the medium might not be rewritable, but a high density, long lasting storage medium would be ideal for back-ups.

Anyway, it's been awhile since I "got out of the business" of chemistry, but this is what I remember.