Holographic data storage with 100 bits//spl mu/m/sup 2/ density

Holographic data storage offers several advantages when compared to conventional storage devices. As a benchmark, we compare holographic memory with optical compact discs. They are both removable, high capacity, and can be randomly accessed. The next generation compact disc due in early 1997, the Digital-Versatile-Disc (DVD), will have a capacity of /spl sim/6 Gbytes per layer, for a maximum planned capacity of /spl sim/20 Gbytes per double-sided disk with two layers on each side. That translates to a surface density of approximately 20 bits//spl mu/m/sup 2/ for the 4 layered DVD disk. In order for holographic 3-D disks to be competitive, we must demonstrate a much higher surface density than the most advanced DVD. A surface density of 100 bits//spl mu/m/sup 2/ was achieved by storing 590000 pixels in each hologram, over an effective hologram area of 5850 /spl mu/m/sup 2/ (7.8 /spl mu/m horizontal displacement /spl times/.75 mm vertical displacement per hologram). The resulting estimated raw bit-error-rate (BER) was approximately 10/sup -4/ and no errors were observed in the sampled hologram when localized threshold values were used. At 100 bits//spl mu/m/sup 2/, we have a comfortable margin over the projected surface density of the most advanced DVD system. Furthermore, the results obtained from this experiment can be applied to a shift multiplexed holographic 3-D disk system. The capacity per 120 mm disk at 100 bits//spl mu/m/sup 2/ is approximately 100 Gbytes.