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Engineers Find a Cheaper Way to Send Data
By DICK STANLEY
c. 1998 Cox News Service
AUSTIN, Texas -- Technical fixes to reduce the World Wide
Wait are coming into use, but a dramatic reduction in their price
could be around the corner because University of Texas engineers
have connected the dots.
Quantum dots, that is: man-made atoms 20,000 times smaller
than the diameter of a human hair. Quantum dots trap electrical
charges, producing lasers for transmitting digital data.
Dennis Deppe, an associate professor of electrical engineering,
and Diana Huffaker, a research associate in electrical engineering,
have for the first time figured out how to make quantum dots
perform as a laser on lower-cost material than they do now.
Moreover, they've done it at the telecommunications industry's
preferred wavelength of 1.3 microns.
The lower-cost material, gallium arsenide, is 10 times cheaper
than the indium phosphide semiconductors now used to make
data-carrying lasers for the fiber-optic technology that increasingly is
used to reduce bottlenecks in the Internet's growing traffic.
''This is a major technical advance,'' said Jack Jewell, a former
AT&T Bell labs researcher who is now chief technical officer of
Picolight Inc., a Boulder, Colo. startup supplier to the
telecommunications industry.
Jewell said the UT achievement is only a laboratory
demonstration whose reliability remains to be worked out, putting it
at least two years away from commercialization.
But he said the breakthrough should be a significant spur to
continued industrial research and development with gallium arsenide
semiconductors.
Making lasers on gallium arsenide could make fiber-optic
technology more readily available to homes and businesses.
In addition to their uses in Internet data transmission, the
cheap lasers could help improve digital video movie discs; the
read/write CDs used by home and business computers; and even bar
code scanners used for such things as tabulating purchases at
checkout counters.
Eventually, Deppe said, quantum dot lasers of gallium arsenide
could be useful when computer chip makers move from wire to
light for transmitting information from chip to chip.
Deppe and Huffaker, researchers at UT's Microelectronics
Research Center, are scheduled to announce their achievement today
at the Semiconductor Science and Technology Conference in La
Jolla, Calif.
They discussed some details of the work last week in an
unscheduled presentation at a telecommunications conference in
Cannes, France.
Available commercial lasers at the 1.3 micron wavelength are
enabling new optical fiber telephone lines to transmit much more
digital information over longer distances, while maintaining truer
sound and sharper images in high-speed applications. They are an
improvement on the older, slower copper telephone cables that have
caused the Internet's World Wide Web to be dubbed the World
Wide Wait.
But the indium phosphide compound used to produce 1.3
micron wavelength lasers - in so-called quantum wells when
stimulated with an electric current - is not only more expensive but
less heat-tolerant than gallium arsenide.
''Because of the significant cost savings, the
telecommunications industry has been pushing hard for a gallium
arsenide laser that operates at this wavelength,'' Deppe said.
Researchers have experimented with quantum dots before, but
making them is tricky. The UT researchers use a process called
molecular beam epitaxy which allows them to make single atomic
layers of a material one at a time.
They used the process to make their quantum dots from
indium gallium arsenide in cavities on a gallium arsenide
semiconductor, similar to the way water droplets form on a shower
curtain.
Huffaker said the atoms assemble themselves in clusters of
about 10 million each in the cavities. When an electric current is
injected into a cavity, the electrons combine with the quantum dots
to generate light. The light bounces back and forth in the cavities,
she said, exciting further emissions of light from the dots, which
produces the laser.
Despite the remaining reliability problems, the UT
development is attracting industry financing for continuing the
18-month-old research that so far has been paid for with a $50,000
grant from the State of Texas Advanced Research program.
''We have a company that's very interested,'' Deppe said.
''But I'm not at liberty to give the name.''
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