Attosecond light gets pulses racing

A discovery of a new way to manipulate light a million times more efficiently than before could open the door to a new sub-branch of photonics - the science of light guidance and trapping.

Photonic crystal fibre technology has produced pulses of light lasting only an attosecond, a billion billionth of a second

A team from the University of Bath have managed to send out pulses of light that last only an attosecond, a billion billionth of a second. Using a special hollow-core photonic crystal fibre - the thickness of a human hair - the team hope to generate light pulses are so brief that they allow researchers to more accurately measure the movement of sub-atomic particles.

Leader of the team, Dr Fetah Benabid, said: “This new way of using photonic crystal fibre has meant that the goal of attosecond technology is much closer. 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.”

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 which traps light and the gas together in an efficient way.

Until now the spectrum produced by photonic crystal fibres has been too narrow for use in attosecond technology, but the team managed to produce a broad spectrum using only a millionth of the power used by non-pcf methods.

With the breakthrough, the team has not only made an important step in applied physics, but has contributed to the theory of photonics. They make 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 what is known as the “photonic bandgap”. Physicists call these modes “bound states”.

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.