Light rambles through room-temperature ruby

In experiments over the past 2 years, physicists have been slowing laser light to a crawl, sometimes even stopping it cold within certain frigid gasses and solids.

Now, researchers at the University of Rochester (N.Y.) have dramatically slowed light within a solid at room temperature–conditions considered vital for slow light to be harnessed for practical uses such as in optical-communication systems.

By firing a specially tuned green laser through a crimson, cigarette-size rod of artificial ruby, Rochester’s Robert W. Boyd and his colleagues have decelerated light pulses to the 57-meter-per-second clip of an express train.

In previous light-slowing schemes (SN: 2/9/02, p. 94: Available to subscribers at Light comes to halt again—in a solid), scientists used two lasers to shuffle electrons in the medium among several energy states. The Rochester team’s approach, reported in the March 21 Physical Review Letters, requires just two energy states and one laser, conditions that bode well for real-world applications, says team member Nick N. Lepeshkin. On the other hand, he notes, to handle the brief light pulses used in optical-communication systems, the team will have to find a substitute for ruby.


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