Scientists build the world's first anti-laser Published duration 17 February 2011

image caption Traditional lasers rely on gain mediums to produce beams of coherent light

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.

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.

image caption 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.