stop light

Scientists may not be able to turn back time, but physicists at Harvard University have stopped light in its tracks. Mikhail Lukin and colleagues have brought light, which normally travels at a phenomenal 186,000 miles per second, to a complete standstill for a fraction of second, they report in the Dec. 11 issue of Nature. Researchers have previously slowed light to a crawl, and light has been halted before, but never without its energy being lost. Lukin’s group is the first to stop a pulse of light with all its energy — its photons — intact. The researchers fired a pulse of red laser light into a cylinder filled with hot rubidium gas and used two control beams whose interaction simulates a surface of tiny mirrors. The light particles are essentially reflected back and forth between the beams so that the light pulse can’t move forward and is “frozen” in place. The researchers held the pulse still for 10 microseconds, and then, by releasing the control beams, allowed it to continue on its merry way.

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 12/23/2003.