February 18, 2011

Scientists Build World’s First Anti-laser

The invention of the laser -- more than 50 years ago -- that has turned up in everything from Compact Discs to laser pointers, now has a new enemy: the "antilaser" -- the first device capable of trapping and terminating laser beams.

The device was created by a team of researchers from Yale University and is capable of absorbing an incoming laser beam entirely. But the antilaser was not developed as a defense against high-power laser weapons, said the researchers.

While such a device seems more like a contraption from a cutting edge science fiction movie, its real-world application will likely be in optical computers, which will be powered by light and electrons, the researchers said on Wednesday.

Professor Douglas Stone and colleagues had initially been developing a theory to explain which materials could be used as the basis of lasers.

Prof Stone explained that recent advances in laser design have resulted in a number of unusual devices that do not fit in the laser-based category. "So we were working on a theory that could predict what could be used to form a laser," he told BBC News.

The theory 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 Stone. The end result? An anti-laser!

Their invention focuses two laser beams of a specific frequency into a specially designed optical cavity made from silicon, which traps the incoming beams and forces them to bounce around until their energy is depleted.

The researchers demonstrated that the anti-laser could absorb 99.4 percent of incoming light, for a specific wavelength.

Altering the wavelength of the incoming light means that the anti-laser can effectively be turned off and on -- and that means it can also be used in optical switches, Stone told the British news company.

Building something which can absorb light over a wide range of wavelengths is pretty simple, but only doing so for a particular wavelength makes the anti-laser potentially useful in optical computing.

The device would not, however, be much use as a laser-shield, said Prof 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."

Besides optical computing, Stone said the technology could ultimately find its way into radiology.

The results appear in the Feb. 18 issue of the journal Science.


Image Caption: In the anti-laser, incoming light waves are trapped in a cavity where they bounce back and forth until they are eventually absorbed. Their energy is dissipated as heat. Credit: Yidong Chong/Yale University


On the Net: