By Will Dunham
Scientists have created a tiny cable -- much thinner than a human hair -- through which they can transmit visible light, potentially paving the way for improvements in solar energy, computing and medicine.
The achievement, described in research published on Monday in the journal Applied Physics Letters, involves a re-imagining of the coaxial cable -- that commonplace conduit of cable television, telephone and Internet service -- on a minuscule scale.
Coaxial cable has been around for decades, prized for its enormously efficient transmission qualities.
It has an inner wire surrounded by an insulator and then another metal sheath. This enables the cable to carry electromagnetic signals with wavelengths bigger than its own diameter.
"We're doing something well known, except we've reduced the dimensions significantly of the coaxial cable," said Michael Naughton, physics department chairman at Boston College and one of the scientists involved in the work.
They fashioned a light-transmitting coaxial cable that contains an inner "wire" of carbon surrounded by an insulator and an outer wire of aluminum. It is about 300 nanometers wide -- several hundred times thinner than a human hair -- with the center wire sticking out at one end to serve as an antenna for light.
Visible light possesses a wavelength of 380-750 nanometers, but the scientists squeezed it through a cable tinier than that. They beamed red and green light through the cable, showing it can transmit a broad spectrum of visible light.
"It's not quite the speed of light, but it's probably 90 percent the speed of light. That's still thousands of times faster than electronics," Naughton said in an interview.
The invention has the potential to lead to numerous technological advances, Naughton added, saying, "It's important because it's useful."
The tiny cable might be used in high-efficiency solar energy cells, Naughton said.
It could lend itself to miniature electrical circuitry and microscopic light-based switching devices for optical computing. It also could have medical applications such as retinal implants for people with the eye disease macular degeneration or detecting single molecules of pathogens in the body, Naughton said.
"You can envision making chips that can move light around -- basically convey information at the speed of light rather than using electronics. So it's optics for the manipulation of information rather than electronics," Naughton said.
Copyright 2007 Reuters Limited.
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