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2011-02-18 07:26:52
Physicists have built the world's first device that can cancel out a laser beam
- a so-called anti-laser.
The device, created by a team from Yale University, is capable of absorbing an
incoming laser beam entirely.
But this is not intended as a defence against high-power laser weapons, the
researchers said.
Instead they think it could be used in next-generation supercomputers which
will be built with components that use light rather than electrons.
Professor Douglas Stone and colleagues at Yale University had initially been
developing a theory to explain which materials could be used as the basis of
lasers.
Strange lasers
Recent advances in laser design have resulted in a number of unusual devices
that do not fit the traditional concept of a laser, Professor Stone explained.
"So we were working on a theory that could predict what could be used to form a
laser," he said.
That theory also predicted that instead of amplifying light into coherent
pulses, as a laser does, it should be possible to create a device that absorbs
laser light hitting it, said Professor Stone - an anti-laser.
They have now succeeded in building one.
What is a laser?
emit light
using an electric current
Their device focuses two lasers beams of a specific frequency into a specially
designed optical cavity made from silicon, which traps the incoming beams of
light and forces them to bounce around until all their energy is dissipated.
In a paper published in the journal Science they demonstrated that the
anti-laser could adsorb 99.4 per cent of incoming light, for a specific
wavelength.
Light speed
Altering the wavelength of the incoming light means that the anti-laser can
effectively be turned on and off - and that could be used in optical switches,
Professor Stone told BBC News.
Depiction of the anti-laser in action The anti-laser could turn out to be more
useful in computing than weapon defence
Building something which can absorb light over a wide range of wavelengths is
pretty simple, said Professor Stone, but only doing so for a particular
wavelength makes the anti-laser potentially useful in optical computing.
The anti-laser's big advantage is that it is built using silicon, which is
already widely used in computing.
It would not, however, be much use as a laser shield, according to Professor
Stone.
"The energy gets dissipated as heat. So if someone sets a laser on you with
enough power to fry you, the anti-laser won't stop you from frying," he said.