(NIST: Gaithersburg, MD) -- Finally, an optical frequency comb that visibly lives up to its name. Scientists at the University of Konstanz in Germany and the National Institute of Standards and Technology (NIST) in the United States have built the first optical frequency comb—a tool for precisely measuring different frequencies of visible light—that actually looks like a comb.

As described in the Oct. 30 issue of Science, the "teeth” of the new frequency comb are separated enough that when viewed with a simple optical system—a grating and microscope—the human eye can see each of the approximately 50,000 teeth spanning the visible color spectrum from red to blue. A frequency comb with such well-separated, visibly distinct teeth will be an important tool for a wide range of applications in astronomy, communications and many other areas.

A basis for the 2005 Nobel Prize in physics, frequency combs are now commonplace in research laboratories and next-generation atomic clocks. But until now, comb teeth have been so closely spaced that they were distinguishable only with specialized equipment and great effort, and the light never looked like the evenly striped pattern of the namesake comb to the human eye.

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