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Thursday, 25 November 2010

Physicists create new type of light

Physicists from the University of Bonn have developed a completely new source of light, previously thought to be impossible - a so-called Bose-Einstein condensate consisting of photons.
The discovery could lead to the development of new light sources resembling lasers that work in the x-ray range, and more powerful computer chips.
By cooling Rubidium atoms deeply and concentrating a sufficient number of them in a compact space, they suddenly become indistinguishable, behaving like a single huge 'super particle' - a Bose-Einstein condensate.
This should also work for photons. Unfortunately, though, there's a fundamental problem: when photons are 'cooled down', they disappear. This is the first time scientists have been able to cool light while concentrating it at the same time.
The Bonn researchers succeeded by using two highly reflective mirrors, bouncing a light beam back and forth between them. Pigment molecules were dissolved between the reflective surfaces; the photons collided with them periodically. In these collisions, the molecules 'swallowed' the photons and then 'spit' them out again.
"During this process, the photons assumed the temperature of the fluid," explains Professor Msrtin Weitz. "They cooled each other off to room temperature this way, and they did it without getting lost in the process."
The physicists then increased the quantity of photons between the mirrors by exciting the pigment solution using a laser. This allowed them to concentrate the cooled-off light particles so strongly that they condensed into a 'super-photon'.
This photonic Bose-Einstein condensate is a completely new source of light that has characteristics resembling lasers. But compared to lasers, they have a decisive advantage.

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