December 12, 2007, Bath, UK--Photonic crystal fiber's ability to create broad spectra of light has been explained for the first time, thanks to research conducted at the University of Bath.
Photonic crystal fiber can change a pulse of light with a narrow range of wavelengths into a spectrum hundreds of times broader and ranging from visible light to the infrared--the supercontinuum. The supercontinuum is one of the most exciting areas of applied physics today, and the ability to create it easily will have a significant effect on technology.
Despite emerging applications for photonic crystal fibers in telecom and optical clocks, the mechanism behind supercontinuum generation has remained unclear, which has stopped physicists from being even more precise in using it. But Dmitry Skryabin and Andrey Gorbach, of the Centre for Photonics and Photonic Materials in the Department of Physics at the University of Bath, have now discovered the reason for much of the broadening of the spectrum.
According to a newly published article in Nature Photonics, they found that the generation of light across the entire visible spectrum was caused by an interaction between conventional pulse of lights and what are called solitons, special light waves that maintain their shape as they travel down the fiber.
The researchers found that the pulses of light sent down the fiber get struck behind the solitons as both pass down the fiber, because the solitons slow down as they move. This barrier caused by the solitons forces the light pulses to shorten their wavelength and so become bluer, just as the solitons' wavelength lengthens, becoming redder. This dual effect creates the broadened spectrum.
"One of the most startling effects of the photonic crystal fibre is its ability to create a strong bright spectrum of visible and infrared light from a very brief pulse of light," Skryabin says. "We have never fully understood exactly why this happens until our research showed how the pulse of light is slowed down and blocked by other activity in the fibre, forcing it to shorten its wavelength."
Until now the creation and manipulation of the supercontinua in photonic crystal fibres have been done in an ad-hoc way without knowing exactly why different effects are observed, he adds. "But now we should be able to be much more precise when using it."
Skryabin believes that the interaction between light pulses and solitons has similarities with the way gravity acts on objects.