Yale University builds world's first anti-laser

Friday, February 18, 2011 

A team at Yale University in the US has built the world's first anti-laser — or coherent perfect absorber (CPA). The device, constructed from silicon, absorbs light and dissipates the energy as heat.

	We couldn't have expected to do any better
—Professor Stone

Professor Hui Cao's researchers were following on from theoretical work last year by Professor Douglas Stone. Stone explained "we were working on a theory that could predict what could be used to form a laser," and the theory also predicted the possibility of an anti-laser. Lasers amplify light to produce coherent pulses.

Laser beams can now be absorbed and turned into heat by anti-lasers

The new anti-laser focuses two identical laser beams towards each other. The light is trapped in an optical cavity and bounces until all the energy is converted into heat. The one constructed by Yale used a piece of silicon 110 micrometers wide; it absorbed 99.4% of light at a wavelength of 998.5 nanometers, which is close to infrared.

Stone felt "[t]heory and experiment matched very well. We couldn't have expected to do any better." The theory suggests that 99.999% could be absorbed, but Yale blamed "experimental limitations" for not achieving this. Yale explained that more sophisticated anti-lasers may approach this absorption rate, and added that simulations suggest much smaller versions could be made.

The research team believes it could have applications in supercomputing, with machines using light and not electrons like regular computers. Many computer components are already manufactured from silicon. Since the energy is dissipated as heat, however, use is limited against laser weapons since the heat would damage the target anyway.

General light-absorption is not difficult, according to Stone, but this is the first time a device has been built targeted to the specific-wavelength beams produced by lasers.

Sources

• "Scientists build the world's first anti-laser" — BBC News Online, February 17, 2011
• Jeff Hecht. "'Anti-laser' built for first time" — New Scientist, February 17, 2011
• Press Release. "Scientists Build World’s First Anti-laser" — Yale University, February 17, 2011