LIGHT MAY SLOW DOWN
Courtesy of Remy Chevalier
LIGHT MAY SLOW DOWN
Courtesy of Remy Chevalier
Roger Highfield, (Science Editor), "Scientists put brakes on light," The Electronic Telegraph, issue 1364, Thursday, 18 February 1999.
Scientists have slowed light down..... way down, reported Dr Lene Hau of the Rowland Institute for Science, and Harvard University. By passing it through an illuminated atomic cloud, they have cut the speed of a pulse of yellow laser light from 186,000 miles per second to 0.01 mile per second and plan to reduce it further to a crawl of about half an inch a second.
Because glass has a refractive index which is larger than that of free space,.light is already known to slow down a little when it enters a piece of glass. Quoted from the magazine: "Dr Hau said: "We are using a much more interesting mechanism to slow light down by a factor of 20 million." The trick is to use one lightbeam to alter the refractive index of an unusual medium - a cloud of sodium atoms cooled to ultra-low temperature known as a "Bose-Einstein condensate" - in such a way that it can slow down a second pulse of light. The trick has a number of applications, Dr. Hau said, such as converting infra-red light into blue light. "In the future, this could be of importance for laser light projectors -- it is hard to generate blue light otherwise."
With a view toward future practicality and commercial applications, such things are suggested as: converting infrared light to the visible spectrum easier, reducing noise in communications, and creating light controlling switches for the new optical computers. Dr. Hau said: "These possible applications are, of course, for the future -- perhaps 10 years down the line if we get to work on it. Right now we have an experimental set-up where we are pushing technology to the outermost limit. We'll have to figure out how to make this into a practical instrument."
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June 2, 1999.