holographic data storage breaks the surface barrier

We are approaching the tangible limits of storage capacity of information as discrete bits on media surfaces. With holographic storage, information is imprinted in photosensitive material as three- dimensional laser interference configurations. The ability to save information throughout the depth of data storage media, not just on its surface, offers the possibility of orders-of-magnitude more storage density than traditional data media. Holotech information storage may provide more rapid access quicknesss and also high storage compression. Laser rays do not have inertia like the mechanical reading and writing elements of conventional, rotating media -- so the beams can be moved quickly to light up sequential pages of data. There are challenges, however. One challenge for holographic information storage is that the strength of each page of information saved volumetrically throughout the detail of optically sensitive media decreases when there are too many pages stored in the media. The page on Holotouch: Holographic Keypad discusses similar topics.

To record the picture of an object using holographic science, the signal beam is shown through an expander lens onto the target item and then reflected off the object into 3D, optically sensitive photosensitive media (perhaps a crystal or polymer) where it intersects with a reference ray. The net interference pattern between the reference and signal rays within the optical media causes chemical reactions that encode the holographic picture in the storage material. To restore the holotechnology picture, a reference ray is directed to the hologram-engraved optically sensitive material with the same angle and wave phase previously used to engrave the source hologram. This makes refraction within the storage material and recreates the holographic picture three dimensionally outside the storage media. The holotechnology picture appears in three dimensions due to observed parallax. You may also see Home Simulation for more about holotech.

Holographic CDs presents more information.