Holographic storage on the horizon

By Lisa Coleman

The race is on to commercialize holographic data storage technology. However, products may still be a few years away.

Holographic storage could enable new applications and hundreds of gigabytes of capacity on a disk the size of a DVD. Some of the first applications of the technology could be in products needing extremely high capacities for archiving data and images. Analysts say that companies requiring data storage for several years, or even decades (such as regulatory agencies that currently use standard optical drives), may find holographic technology useful for permanent data recording. In addition, the technology could be a draw for manufacturers of portable consumer devices.

Holographic technology significantly increases areal densities compared to current optical and magnetic technologies. Holographic storage will have areal densities around 300Gb per square inch, whereas current optical technology, for example, ranges between 70Gb and 80Gb per square inch.

Potentially, holographic storage could surpass both magnetic and optical technology in capacity, data access speed, and transfer rates, according to Skip Kilsdonk, vice president of business development at Longmont, CO-based InPhase Technologies, a Bell Labs spin-off that is developing holographic storage products.

Holographic recording stores data on a polymerizable storage medium. Data is recorded by an optical interference pattern created by mixing an encoded data beam. Data is encoded as two-dimensional binary pages of bright and dark spots using a spatial light modulator (SLM). For reading data, a laser beam is projected onto the recorded interference pattern in the medium. The transmitted beam, carrying a reconstructed data page, is imaged onto a detector similar to the SLM.
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Using optics and "polymerizable" storage medium, holographic technology records data as two-dimensional binary pages through the three dimensions of the media. Unlike magnetic media, which allows recording only on a disk's surface, the entire thickness of holographic media can be used. An optical interference pattern is recorded onto the media using a laser, and the data is retrieved via a laser beam that is projected onto the pattern. Then, the transmitted beam carrying the reconstructed data page is imaged onto a detector that can read the resulting light/shadow patterns as binary code.

InPhase is developing holographic storage products using its proprietary media and a manufacturing process called ZeroWave. InPhase officials expect product development to take "a couple of years."

Another company working on holographic storage products is Cambridge, MA-based Aprilis, a spin-off of Polaroid. In November 2000, the company demonstrated a 1Gbps data recording rate when Stanford University tested its media for the Defense Advanced Research Projects Agency (DARPA), which sponsored research to develop holographic systems. Aprilis expects to have a prototype available within two years.

Media is the key for holographic product differentiation, according to vendors. "We believe that a major difference in performance will result from differences in the media," says Glenn Horner, vice president of business development at Aprilis. Performance disparities may also depend on recording geometries, optical design, and system overhead.

This article was originally published on February 01, 2002