Scientists and engineers at Yale University have just created an anti-laser, a device which absorbs light. Instead of shooting energy out of a tube, it takes energy into a tube. Instead of creating light, it creates darkness. How does it work?
Lasers start out in a tube that is mirrored on both sides. When energy is forced into the tube, the material inside gets excited. The electrons in the atoms of the material jump up a level, and then fall back down. When they do, they emit a photon, which starts travelling around the tube. It bounces off the mirrors on both sides, getting in phase with all the other protons in the tube. Generally, the mirror on one side of the tube is only half-silvered, so eventually the photons find an opening and march out in a directional, single-wavelength beam of light. [via io9]