Velcroman1 writes "Two scientists at Yale University have built the laser's first doppelganger: the anti-laser. While a conventional laser emits a constant beam of light in one direction, the anti-laser simply does the opposite. It takes that same steady light stream and interacts with it in such a way that it absorbs and cancels out the light. And scientists hope the strange creation could help the fight against cancer. A. Douglas Stone, one of the two researchers behind the project, said he came up with the idea for a 'nega-laser' when working with equations for a random laser with his partner in crime, Hui Cao. 'I figured, if we just somehow illuminated the cavity, and replaced the gain medium with something that tends to absorb light, we could essentially reverse the process,' Stone said. Oh, that makes sense."