This amazing information was shared with us courtesy of Doug Renner.
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Hello Jerry! Here's some very impressive news...
http://www.nytimes.com/library/national/science/021899sci-slow-light.html
(C) New York Times
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February 18, 1999
In a Major Breakthrough, Danish Physicist Slows the Speed of Light
By MALCOLM W. BROWNE
When light travels through empty space, it zips along at a speed of
186,171 miles a second -- the highest speed anything can attain, even in
principle. A moonbeam takes only a little over one second to reach
Earth.
But a Danish physicist and her team of collaborators have found a way to
slow light down to about 38 miles an hour, a speed exceeded by a strong
bicyclist.
The physics team, headed by Dr. Lene Vestergaard Hau, who works
concurrently at the Rowland Institute for Science in Cambridge, Mass.,
and at Harvard University, expects soon to slow the pace of light still
further, to a glacial 120 feet an hour -- about the speed of a tortoise.
"We're getting the speed of light so low we can almost send a beam into
the system, go for a cup of coffee and return in time to see the light
come out," Dr. Hau said in an interview.
The achievement, by Dr. Hau, two Harvard graduate students and Dr. Steve
Harris of Stanford University, is being reported on Thursday in the
journal Nature.
Physicists said it had many potential uses, not only as a tool for
studying a very peculiar state of matter but also in optical computers,
high-speed switches, communications systems, television displays and
night-vision devices.
One of the most desirable features of the apparatus that the researchers
built for their work is that it does not transfer heat energy from the
laser light it uses to the ultracold medium on which the light shines.
This could have an important stabilizing effect on the functioning of
optical computers, which operate using photons of light instead of
conventional electrons.
A switch using the system could be made so sensitive that it could be
turned on or off by a single photon of light, Dr. Hau said.
The medium Dr. Hau and her colleagues used in slowing light by a factor
of 20 million was a cluster of atoms called a "Bose-Einstein condensate"
chilled to a temperature of only fifty-billionths of a degree above
absolute zero.
(Absolute zero is the temperature at which nothing can be colder. It is
minus 273.15 degrees on the Celsius scale, minus 459.67 on the
Fahrenheit scale and zero on the Kelvin scale.)
Dr. Hau's group reached an ultralow temperature in stages, using lasers
to slow the atoms in a confined gas and then evaporating away the
warmest
remaining atoms. The temperature they attained, one of the lowest ever
reached in a laboratory, was far colder than anything in nature,
including the depths of space.
Bose-Einstein condensates (named for the theorists who predicted their
existence, Satyendra Nath Bose and Albert Einstein) were first prepared
in a laboratory four years ago and became the objects of intense
research in the United States and Europe. They owe their existence to
some of the rules of quantum mechanics.
One of these is Werner Heisenberg's uncertainty principle, which states
that the more accurately a particle's position is known, the less
accurately its momentum can be determined, and vice versa.
In the case of a Bose-Einstein condensate, atoms chilled nearly to
absolute zero can barely move at all, and their momentum therefore
approaches zero. But because zero is a very precise measure of momentum,
the uncertainty principle makes the positions of these atoms very
uncertain.
In a condensate, as a result, such atoms are forced to overlap each
other and merge into superatoms sharing the same quantum mechanical
"wave function," or collection of properties.
It was such a superatom, made of a gas of superpositioned sodium atoms,
that provided Dr. Hau and her associates with the optical molasses they
needed to slow light down.
Beginning their project last spring, the group tuned a "coupling" laser
to the resonance of the atoms in their condensate, shot the laser into
the cold cluster of atoms and thereby created a quantum mechanical
system of which both the laser light and the condensate of atoms were
components. At this stage, the system was no more transparent than a
block of lead, Dr. Hau said.
The next step was to send a brief pulse of tuned laser light from a
"probe" into the condensate, at a right angle to the coupling laser, in
such a way that the laser-condensate system interacted with the probe
laser. Under these conditions about 25 percent of the probe laser light
passed through the "laser-dressed condensate," but at an astonishingly
slow speed.
The light that emerged from the apparatus, not visible to the naked eye,
was only 25 percent as strong as the light that entered, but detectors
found that it had roughly the same color.
The speed of light is reduced in any transparent medium, including
water, plastic and diamond. Glass prisms and lenses, for example, slow
light by
differing amounts that depend on the thickness of the glass. The slowing
of light causes the bending by which lenses focus images.
But the reduction of light speed in a laser-coupled Bose-Einstein
condensate works in an entirely different, quantum-mechanical way. Not
only is the speed brought to a crawl, but the refractive index of the
condensate becomes gigantic.
Refractive index is a measure of the degree to which a medium bends
light. The refractive index of the condensate created by Dr. Hau's group
was about 100 trillion times greater than that of a glass optical fiber.
Although Dr. Hau said it might take 10 years before major applications
were developed, the huge refractive index of the condensate, which can
be
precisely controlled, may make it a basis for "up shifting" devices that
increase the frequencies of light beams from the infrared end of the
spectrum up through visible light to ultraviolet.
Possible applications include ultrasensitive night-vision glasses and
laser light projectors that could create very bright projected images.
Laser-condensate combinations may also lead to ultrafast optical
switching systems useful in computers that would operate using one light
beam to control another light beam.
Such a system could function as an optically switched logic gate,
replacing the electronic logic gates computers now use.
Slow light could also be exploited in filtering noise from optical
communications systems, Dr. Hau said.
Dr. Jene Golovchenko, a physics professor at Harvard familiar with Dr.
Hau's work, commented, "She has worked long and hard on this, and now
she's really hit a home run."
-- Jerry Wayne Decker / jdecker@keelynet.com http://keelynet.com / "From an Art to a Science" Voice : (214) 324-8741 / FAX : (214) 324-3501 KeelyNet - PO BOX 870716 - Mesquite - Republic of Texas - 75187