Glowing Butterflies Shine With Natural LEDs

November 17, 2005

For 30 million years African swallowtail butterflies have dazzled their mates with glowing splashes of color on their wings (see photo). And the process they use to control the flow of light in their wings is strikingly similar to a technology that humans only recently developed, physicists report.

From the lasers used to read information on CDs and DVDs to the data carried across oceans along optical fibers, the control of light is essential to modern living.

One way scientists control light is through the use of light emitting diodes (LEDs). These electronic devices are made out of semiconductor material—a type of solid substance that can conduct electricity—that lights up when a current passes through them.

LEDs are found in traffic lights, computer screens, car brake lights, and many other gadgets that flash color without the use of a conventional light bulb.

But physicists had long deemed traditional LEDs inefficient, because most of the light they created was unable to escape the semiconductor material. All the generated light rays that went sideways or downward, for example, were essentially lost.

Improved LEDs

After years of research, physicists recently overcame these limitations with "high-efficient LEDs." The new breed of LEDs uses specialized mirrors and tiny structures called photonic crystals to generate more usable light from the semiconductor materials.

Pete Vukusic and Ian Hooper, physicists at the University of Exeter in the U.K., report that nature perfected this method in the African swallowtail butterfly long ago.

The butterfly has natural versions of these specialized mirrors and photonic crystals, which brighten the fluorescent blue and green splotches on their wings.

"The analogy is to the way light is extracted from both systems, which is really exciting, it is amazing," Vukusic said. He and Hooper report the discovery in tomorrow's issue of the journal Science.

Alexei Erchak is the founder of Luminus Devices in Woburn, Massachusetts. While a graduate student at the Massachusetts Institute of Technology in Cambridge, he developed the first prototype high-efficient LED in 2001.

Erchak said he is "amazed" at the similarity between the structure in the butterfly wing and his own LEDs.

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