The growth in demand for digital storage capacity exceeds 60% per annum. Facilities such as storage area networks, data warehouses, supercomputers and e-commerce, e- related data mining, require ever greater capacity in order to handle the volume of data to be processed.
In addition, with the advent of high bandwidth Internet and data-intensive applications such as high-definition TV (HDTV) and video and music on-demand, even smaller devices such as personal VCRs, PDAs, mobile phones, etc., will, in the next couple of years, demand multi-gigabyte and terabyte capacities. No less important is the growing demand for faster data access and reading. For instance, high-definition TV and video and music-on-demand applications require over terabit/s reading speed.
Such higher speeds in conjunction with huge capacity can be implemented only by means of parallel access to any part of information on the carrier. While the limits of magnetic recording are still being debated, the limits of conventional optical storage are well understood. Future increases in density are possible by taking advantage of shorter wavelength lasers, higher lens numerical aperture (NA), or by employing near-field techniques. Finally, optical data storage capacities have been increased by creating double-sided media. Another approach to increasing the effective storage capacity is quite unique for optical memory technologies. This is three-dimensional storage.
True three-dimensional optical storage opens up another dimension in which to increase the capacity of a given volume of media, with the objective of achieving a cubic storage element having the dimensions of the writing /reading laser wavelength. Even with current wavelengths of 650 ?m, this should suffice to store up to a Terabytes of data...