Home' Technology Review : September 2005 Contents 66 FEATURE STORY
consumer electronics over the last few years---and much of the
economic health of the industry---are directly traceable to the ex-
plosion in storage capacity. Web e-mail ser vices routinely o er
each of their customers a gigabyte of memory for free. Apple's
newest iPod is only possible because of small, cheap hard drives
that can hold a staggering 60 gigabytes of data---a storage capac-
ity that just ve years ago would have been a lot for a desktop PC.
Likewise, cell phones now come with ash memory chips easily
able to store address books, calendars, photos, and the like.
Meanwhile, CDs and DVDs have already transformed how peo-
ple listen to music and watch movies. But each of these storage
technologies has drawbacks. The density of magnetic materials
in hard drives is fast approaching a fundamental physical limit.
Flash memory is slow, and a DVD is barely large enough to hold
a full-length movie.
Storing data in three dimensions would overcome many of
these limitations. Indeed, the theoretical promise of holographic
storage has been talked about for 40 years. But advances in
smaller and cheaper lasers, digital cameras, projector technolo-
gies, and optical recording materials have nally pushed the
technology to the verge of the market. And the ability to cram
exponentially more bits into in nitesimal spaces could open up
a whole new realm of applications.
By storing and reading out millions of bits at a time, a holo-
graphic disc could hold a whole library of lms. Movies, video
games, and location-based services like interactive maps could
be put on postage-stamp-size chips and carried around on cell
phones. A person's entire medical history, including diagnostic
images like x-rays, could t on an ID card and be quickly trans-
mitted to or retrieved from a database. Eventually, if the hard-
ware becomes a ordable for consumers, holographic storage
could supplant DVDs and become the dominant medium for
games and movies. Portable movie players and phones that
download multimedia from the Web would take o . Holographic
storage could even compete with the magnetic hard drive as the
computer's fundamental storage unit. And on a larger scale, cor-
porate and government data centers could replace their huge,
raucous storerooms of ser ver racks and magnetic-tape reels with
the quiet hum of holographic disc drives.
InPhase's competitive edge lies in its partnerships with Hita-
chi Maxell, a leading producer of computer tapes and CD-
ROMs, and---as of this May---Bayer MaterialScience, one of the
world's largest makers of plastics used in optical discs. These
large corporations see holographic techniques as the next step
in the evolution of storage. "Our collaboration with InPhase
gives us a tremendous opportunity," says Hermann Bach, head
of technologies for the Americas at Bayer MaterialScience.
But if and when holographic storage will come to dominate
the market is still an open question. InPhase's initial product
launch is slated for late 2006, but industry experts, while opti-
mistic, are also cautious. "They have made numerous contribu-
tions on the hardware side, in media and materials, and in error
correction," says Hans Coufal, manager of science and technol-
ogy strategy at IBM's Almaden Research Center in San Jose,
CA, and an expert on holographic storage. "It's very impressive
but still some ways away from a viable product. Not a long ways,
but some ways."
The idea of holographic storage dates back to the work of Pola-
roid researcher Pieter J. van Heerden in the early 1960s (and,
some contend, to Nobel laureate Dennis Gabor's original theory
of holography in 1948). But the technology had never been prac-
tical, requiring exceedingly expensive materials and bulky laser
setups---unlike the streamlined system from InPhase. Even Bill
Wilson, InPhase's chief scientist, was originally skeptical. In
1987, as a fresh PhD in physical chemistry from Stanford Univer-
sity, Wilson joined Bell Labs, turning down a job at IBM, where
he would have started working on holographic storage. "I
thought the eld would be a complete waste of time," he admits.
The turnaround began in the early 1990s, when IBM and other
big players started to worry about the limitations of magnetic stor-
age. As storage capacity increases, the magnetic grains that store
data on a hard drive get packed closer together. Eventually, each
grain's magnetic eld will begin to interfere with those of its
neighbors, hindering their ability to reliably hold data. Engineers
have thought of clever ways to defer this problem, but ultimately,
grains in magnetic materials will be too dense to work properly.
Wilson recalls jumping into a friendly argument in the Bell
Labs lunchroom about what new technology could eventually
take the place of magnetic media---and the relative merits of holo-
graphic storage. At the time, the technique was undergoing
something of a revival, being investigated by research groups at
IBM, Polaroid, Caltech, and Stanford. Wilson and Kevin Curtis,
an electrical engineer from Caltech who had recently joined Bell
Labs, argued that holographic storage might actually become vi-
able with suitably small and cheap optical components. In dis-
cussing the technical issues with their colleagues, they realized
the key to making it viable was the material that stored the data.
In holographic storage, a "data beam" holding information is
crossed with a "reference beam" to produce an interference pat-
ter n that's recorded in a light-sensitive material. To retrieve data
from a particular spot, a reference beam is shone onto it, and the
combination of the reference beam and the patterned material
reconstructs the original data beam, which is read by a digital-
camera detector that translates the beam into a series of electrical
signals. The recording material is typically either an inorganic
crystal or a polymer. Polymers are more sensitive and require
less powerful lasers, but they have their own aws. For instance,
when you hit a photosensitive polymer with a laser, it tends to de-
form, which messes up the data.
In 1994, a materials team at Bell Labs led by chemist Lisa Dhar
worked with Wilson and Curtis to produce a "two-chemistry"
photosensitive polymer. The researchers mixed one sca oldlike
polymer, which stayed rigid and preserved its structure, with an-
other polymer that reacted to light and stored data. Decoupling
the recording material's optical and structural properties let the
researchers ne-tune each independently, arriving at a combina-
tion of sensitivity and stability that had eluded previous e orts.
Over the next four years, the Bell Labs team got its holo-
graphic material to work in conjunction with the latest miniatur-
ized lasers, cameras, and optical components to read and write
data. This also required advances in software to correct for er-
rors in storing and retrieving digital bits. In 1998, as a proof of
concept, they built a prototype holographic recorder and re-
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