Holographic storage nears debut

or more than 20 years researchers worldwide have pursued the Holy Grail of holographic data storage, an optical method of storing massive amounts of data in small areas by writing data as light patterns in three dimensions on a filmlike medium.

During that time, hardware advances carried out independent of holography have made holographic storage more achievable. These include such improvements as CMOS sensor technology, development of spatial light modulators using ferroelectric liquid crystals and mirror arrays, and reduction in the cost and size of shorter wavelength green lasers. Yet the biggest challenge has been to find the right material for the recording medium, one that works and is inexpensive enough to produce commercially.

In the last year, some research groups at universities, corporations, government labs and startups claimed to have found the material that will propel the technology forward and enable its adoption in commercial storage media products in two to three years.

However, storage industry analysts have a different view of when holographic storage will become reality.

Jim Porter, president of DiskTrend Inc., a storage industry research firm in Mountain View, Calif., said the holographic storage announcements he's heard have been mostly smoke and no fire, none of them having discussed specific products, and few offering realistic timelines for commercial availability.

In fact, Porter disagreed with the characterization of holographic storage as an "emerging" market, saying it's more of a nonexistent market.

Analysts such as Porter may be cynical about near-term expectations for the technology, but researchers in the field can't be more enthused about its prospects.

Rob Hermes, chief scientist working on holographic data storage at HoloStor, a division of Manhattan Scientific Inc. in Los Alamos, N.M., described research activity in this field as very hot and called it a "race" to create a good, inexpensive photopolymer.

Hermes is a polymer scientist who joined HoloStor a year ago after working at Los Alamos National Laboratories. He is perfecting a photopolymer that was originally developed by the government-funded MCC consortium in Austin, Texas in the 1980s that set out to develop systems for holographic data storage. The intellectual property was sold to Tamarack Storage Devices and finally ended up in the hands of businessman/executive Marvin Maslow, who founded Manhattan Scientific, and formed the HoloStor unit in 1998.

The firm owns more than 20 patents, including one for a photopolymer formulation that would form the basis for holographic media. This formulation is a proprietary mixture of nine components that Hermes claims has the required sensitivity or film speed, and the dynamic range (capacity) to be useful for storing several pages of data containing 1 million bits on each page.

To make holographic storage competitive, though, Hermes said, the medium must store a minimum of 100, 1 million-bit page images and eventually 1,000 page-images to rival existing technologies.

Today, Hermes works to enhance the formulation so that it has improved image quality (sharpness) and subsequent readability. HoloStor is targeting image lifetimes of 10 to 20 years, and proof that it can multiplex many images in the same spot or location (the 3-D part of holographic data storage).

Hermes said tests performed on the material at a facility he declined to name showed HoloStor's formulation to be good, but not exceptional-a requirement for commercial development-something he said is still three to five years away.

Spin-off at work
Meanwhile, researchers at Aprilis Inc. (Cambridge, Mass.), a Polaroid-spin-off that is developing holographic data storage systems, licensed a polymer patented by Polaroid that is based on epoxy-modified silicones. The material is based on Crop (cationic ring opening polymerization) chemistry.

According to Aprilis' vice president of research and development David Waldman, Crop solves the problem of volume shrinkage associated with conventional photopolymers formed by free-radical polymerization chemistry.

Volume shrinkage occurs when a photopolymer activated by laser light shrinks in volume as it moves from liquid to solid state and optically throws off the pixels recorded in the hologram to impair the image's fidelity. It is one of the bugaboos that's hindered the development of holographic media.

Aprilis' material was chosen to be the write-once holographic recording media in three public demonstrations of holographic data storage systems, including one at Stanford University in November 2000. That demonstration involved several companies in the Holographic Data Storage System (HDSS), a DARPA-funded group that includes IBM Corp.'s Almaden Research Center (San Jose, Calif), Rockwell Science Center (Thousand Oaks, Calif.) and Stanford University.

The demo achieved data rates of 6 Gbits per second with megapixel data pages, a good result.

Aprilis recently received a multimillion-dollar investment from venture firm Zero Capital (Cambridge) and is pursuing collaborative development of holographic storage systems by licensing technology from other players in the United States and abroad.

Waldman said the company intends to commercialize both the holographic recording media and a holographic storage technology system in approximately two years.

Another startup in the race to provide a solution to the holographic media conundrum is InPhase Technologies, a Longmont, Colo., group launched out of Lucent Technologies in January. InPhase aims to commercialize technology based on a photopolymer material developed at Bell Laboratories, and storage media and manufacturing technology co-developed by Lucent and Imation Corp. (Oakdale, Minn.) under a 1999 agree-ment. InPhase gains access to these technologies via a license from Lucent.

The company's technology rests on the invention of a photopolymer with bit-storage characteristics and environmental ruggedness suitable for extreme temperature and humidity. In a 1999 interview with EE Times, InPhase Technologies' chief technology officer, Kevin Curtis, said the material possessed "more sensitivity and better dynamic range than lithium niobate," the preferred material at the time. No time line had been set for the introduction of products, and it was not clear which storage markets the business would target.

But two years later, in a January 2001 interview, the company's president and chief executive, Nelson Diaz, said he believes the technology will enable "point-of-sale kiosks" where consumers would purchase movies stored on very cheap media, or be incorporated into information systems for data archiving and retrieval. Development of commercial products is under way, but at least two years off.

Down to earth
As enthusiastic as the researchers are about holographic storage media, analysts are quick to bring their claims down to earth.

DiskTrend's Jim Porter said holographic storage media will have limitations at the get-go because most researchers say the first products will be write-once, read-many-times, rather than rewritable media. "Because the first products will be write-once, it means the first holographic storage media won't affect what you're doing today with magnetic-tape or magnetic-disk technology," Porter explained.

Write-once, read-many optical drives have a limited and specialized use in government and financial applications. These applications involve data being stored on media in robotic-driven libraries such as government storage of its huge Social Security database, where having three-dimensional storage would be more cost-effective than existing technologies. Porter said he could also envision the technology being deployed in banks or financial institutions, where the holographic media would enable a storage system that would let bank employees access images of checks on terminals instantaneously in offices worldwide. For the long run, Porter said he'd have to "wait a few years to see. I go by results, not promises."

In the meantime, Constellation3D Inc. (New York), a developer of a new optical-storage media called Fluorescent Multilayer Disc (FMD), is creating technology it claims could enable large storage densities that go beyond compact disk and DVD, but fall short of holographic storage's promises. The company's technology is based on a fluorescent dipolymer as a coating for each storage layer on a CD-sized disk.

Company secret
The fluorescent material remains a company secret, but was described to EE Times as an inexpensive material commonly used in food processing. A Russian chemist and expert in photochemistry invented the technology along with several colleagues who founded the firm in 1995. With researchers in Israel, Florida and Russia, the company is betting the technology will capture the interests of Hollywood and high tech.

John Ellis, the company's vice president of marketing, said his organization would demonstrate a DVD pit-density ROM disk with a 20-Mbit per second transfer rate in June 2001. In February 2001, Constellation3D inked a deal with Plasmon plc of London, a provider of recordable optical-disk technology, to develop production processes for mass production of FMD media. The company said it also signed letters of intent to work with manufacturers of CD-ROM drives, as well as equipment providers and a chemical film company.

Wolfgang Schlichting, an analyst covering removable storage at International Data Corp. (Framingham, Mass), said FMD technology has significant potential, "but the company will need partners to commercialize it in a big way." He said the company faces engineering challenges that it won't know about until it begins manufacturing. For that reason, the technology "has a long way to go."