
Discovery of a new way to manipulate light a million times more efficiently
Date: Saturday, November 17, 2007 @ 21:18:02 UTC Topic: Science
A discovery of a new way to manipulate light a million times more efficiently than before is announced in the journal Science this week.
Using a special hollow-core
photonic crystal fibre, a team at the University of Bath, UK, has
opened the door to what could prove to be a new sub-branch of
photonics, the science of light guidance and trapping.
The team, led by Dr Fetah Benabid, reports on the discovery, which
relates to the emerging attotechnology, the ability to send out pulses
of light that last only an attosecond, a billion billionth of a second.
These pulses are so brief that
they allow researchers to more accurately measure the movement of
sub-atomic particles such as the electron, the tiny negatively-charged
entity which moves outside the nucleus of an atom. Attosecond
technology may throw light, literally, upon the strange quantum world
where such particles have no definite position,only probable locations.
To make attosecond pulses, researchers create a broad spectrum of light from visible wavelengths
to x-rays through an inert gas. This normally requires a gigawatt of
power, which puts the technique beyond any commercial or industrial
use.
But Dr Benabid’s team used a photonic crystal fibre (pcf), the
width of a human hair, which traps light and the gas together in an
efficient way. Until now the spectrum produced by photonic crystal
fibre has been too narrow for use in attosecond technology, but the
team have now produced a broad spectrum, using what is called a Kagomé
lattice, using about a millionth of the power used by non-pcf methods.
“This new way of using photonic crystal fibre has meant that the
goal of attosecond technology is much closer," said Dr Benabid, of the
University of Bath’s Department of Physics, who worked with students Mr
Francois Couny and Mr Phil Light, and with Dr John Roberts of the
Technical University of Denmark and Dr Michael Raymer of the University
of Oregon, USA.
“The greatly reduced cost and
size of producing these phenomenally short and powerful pulses makes
exploring matter at an even smaller detail a realistic prospect.”
Dr Benabid’s team has not only made an important step in applied
physics, but has contributed to the theory of photonics too. The
effectiveness of photonic crystal fibre has lain so far in its
exploitation of what is called photonic band gap, which stops photons
of light from “existing” in the fibre cladding and enabled them to be
trapped in the inside core of the fibre.
Instead, the team makes use of the fact that light can exist in
different ‘modes’ without strongly interacting. This creates a
situation whereby light can be trapped inside the fibre core without
the need of photonic bandgap. Physicists call these modes bound states
within a continuum.
The existence of these bound states between photons was predicted
at the beginning of quantum mechanics in the 1930s, but this is the
first time it has been noted in reality, and marks a theoretical
breakthrough.
Source: University of Bath Via: http://www.physorg.com/news114438000.html
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