A team of physicists from Yale University has built the world's first anti-laser device capable of absorbing an incoming laser beam. The incoming laser beam is absorbed entirely such that it is canceled out. However, the device is not intended as a defense mechanism against high-power laser weapons but instead will prove useful in next-generation supercomputers built with components using light rather than electrons.
As for an overview of how the device works, let's quote BBC based on what Professor Douglas Stone revealed to them: "The device focuses two laser 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." The device can absorb 99.4 percent of incoming light for a specific wavelength.
Professor Stone also said that the anti-laser would be most useful in optical computing with a big advantage being its use of silicon which is already widely used in computing. However, he reiterates that the device is not meant for defense against high powered laser weapons. He goes on to say, "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."
[Via BBC News]