Fast high-density disk storage by multiplexed microholograms

The new concept of microholographic data storage allows storage capacities of up to 100 GB on a DVD-sized disc 11/. This concept involves bitwise information storage similar to CD and DVD systems. Instead of using pits, the information is coded in form of holographically recorded, microscopic Bragg-reflectors, located in a thin, photosensitive layer (Fig. 1). Each microholographic Bragg-reflector represents one bit, presuming no coding scheme is applied. Microholograms can be stored overlapping in the same volume by using angle multiplexing, wavelength multiplexing or the combination of both. Such storage of multiple information bits in one single position on the disc increases the storage capacity as well as the data transfer rates by the multiplex factor. In contrast to previous holographic storage systems, the storage media are made of cheap and mass-produceable photopolymer layers instead of expensive crystals. Furthermore, the microholographic storage method can be downward compatible with today's Compact-Disk (CD)- and Digital-Versatile-Disk (DVD) systems.