Light is fast and that is handy, but engineers building computers that use light rather than electrons need to slow it down on occasion. It wouldn’t do any good, for instance, to add two numbers before one of them had even arrived. In November two physicists revealed a way of creating a sort of optical molasses that can slow light in an optical fiber down to a crawl.
Dick Slusher and Ben Eggleton of Bell Laboratories in Murray Hill, New Jersey zapped a two-inch stretch of optical fiber with ultraviolet light at 150,000 evenly spaced points. The radiation damaged the fiber slightly and increased its index of refraction at each point, creating a grating made of, as Eggleton puts it, 150,000 tiny mirrors. Each mirror reflected only a small portion of light coming through the fiber, but in combination they showed some interesting results.
In particular, when the light’s wavelength ...
