New Scientist: "Light 'frozen' in its tracks
18:00 10 December 03
NewScientist.com news service
A pulse of light has been stopped in its tracks with all its photons intact, reveal US physicists.
In a vacuum, light travels at the phenomenal speed of 300,000,000 metres per second. Scientists can exploit the way that the electric and magnetic fields in light interact with matter to slow it down.
Over the last few years, scientists have become masters of the light beam. Speeds of a few metres per second are now reached routinely in laboratories around the world. It is rather harder, however, to stop light completely and previous attempts have halted light but lost its photons in the process.
Mikhail Lukin and colleagues at Harvard University in Cambridge, Massachusetts managed to stop light without this loss by firing a short burst of red laser light into a gas of hot rubidium atoms.
This is then 'frozen' with the help of two control beams. The light in the control beams interacts with the rubidium atoms to create layers that alternately transmit and reflect the pulse.
As the signal tries to propagate through these layers, the photons bounce backwards and forwards between them. As a result, the pulse makes no forward progress - the light is 'frozen' in place. The pulse is set free when the control beams are turned off.
Ulf Leonhardt at the University of St Andrews in Fife, Scotland, says the technique is novel in that the effect the control beams have is 'like storing light behind bars'."
18:00 10 December 03
NewScientist.com news service
A pulse of light has been stopped in its tracks with all its photons intact, reveal US physicists.
In a vacuum, light travels at the phenomenal speed of 300,000,000 metres per second. Scientists can exploit the way that the electric and magnetic fields in light interact with matter to slow it down.
Over the last few years, scientists have become masters of the light beam. Speeds of a few metres per second are now reached routinely in laboratories around the world. It is rather harder, however, to stop light completely and previous attempts have halted light but lost its photons in the process.
Mikhail Lukin and colleagues at Harvard University in Cambridge, Massachusetts managed to stop light without this loss by firing a short burst of red laser light into a gas of hot rubidium atoms.
This is then 'frozen' with the help of two control beams. The light in the control beams interacts with the rubidium atoms to create layers that alternately transmit and reflect the pulse.
As the signal tries to propagate through these layers, the photons bounce backwards and forwards between them. As a result, the pulse makes no forward progress - the light is 'frozen' in place. The pulse is set free when the control beams are turned off.
Ulf Leonhardt at the University of St Andrews in Fife, Scotland, says the technique is novel in that the effect the control beams have is 'like storing light behind bars'."
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