Boffins plug in super-thin coax

Boffins at Boston College in the US have beamed visible light through a cable hundreds of times thinner than a human hair.

The discovery defies a key principle asserting that light cannot pass through a hole much smaller than its wavelength.

Scientists have managed to force visible light, which has a wavelength of 380nm-750nm, to travel down a cable with a diameter smaller than even the low end of this range.

The researchers say their achievement could lead to new developments including inexpensive high-efficiency solar cells and microscopic light-based switching devices for use in optical computing, or even helping some blind people to see.

"Our coax works just like the one in your house, except now for visible light," said Jakub Rybczynski, a research scientist in the Boston College Physics Department.

Coaxial cables are typically made up of a core wire surrounded by a layer of insulation, which in turn is surrounded by another metal sheath.

This structure encloses energy and lets the cable transmit electromagnetic signals with wavelengths much larger than the diameter of the cable itself.

The physicists have developed what they called a nanocoax, a carbon nanotube-based coaxial cable with a diameter of about 300nm.

"The beauty of our nanocoax is that it lets us squeeze visible light through very small geometric dimensions. It also allows us to transmit light over a distance that is at least 10 times its wavelength," said fellow researcher Kris Kempa.

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