01.jpgMuch to the distaste of James Bond villains everywhere, scientists from Yale University recently demonstrated not a new, more powerful type of laser, but actually its opposite – the world’s first anti-laser. The device receives incoming beams of light, which interfere with one another in such a way as to cancel each other out. It could apparently have valuable applications in a number of technologies, such as opticalcomputing and radiology.
Lasers work by using a “gain medium,” often gallium arsenide or some other semiconductor, to produce light waves with the same frequency and amplitude. These waves, which are in step with one another, make up a focused beam of coherent light.
By contrast, the anti-laser utilizes a silicon wafer “loss medium.” When two laser beams were shone into a cavity containing that wafer, it aligned the light waves so that they became “perfectly trapped,” causing them to ricochet back and forth until they were absorbed and transformed into heat.
The anti-laser, officially known as a coherent perfect absorber (CPA), is about one centimeter across, and capable of absorbing 99.4 percent of incoming light. According to Yale physicist A. Douglas Stone, however, the current model is merely a proof-of-concept. He believes that future versions should be able to absorb 99.999 percent of the light, and could be built as small as six microns – approximately one-twentieth the width of a human hair. The current CPA is also limited to absorbing near-infrared light, but Stone believes that by altering the cavity and the loss medium, future versions should be able to handle visible and infrared light.
CPAs could reportedly find use in optical computers, serving as components such as optical switches or detectors. Stone believes they could also be used in radiology, where they could focus electromagnetic radiation to a small region within opaque human tissue, for imaging or therapeutic purposes.
