Optical fibre laser spots disease and greenhouse gases

Published in Optics Letters, the researchers from the University’s Institute for Photonics and Advanced Sensing and the School of Chemistry and Physics describe how they have been able to produce 25 times more light emission than other lasers operating at a similar wavelength, which could lead to the detection of very low concentrations of gases.

‘This laser has significantly more power and is much more efficient than other lasers operating in this frequency range,’ said Ori Henderson-Sapir, PhD researcher in a statement. ‘Using a novel approach, we’ve been able to overcome the significant technical hurdles that have prevented fibre lasers from producing sufficient power in the mid-infrared.’

The new laser operates in the mid-infrared frequency range, which is the same wavelength where many important hydrocarbon gases absorb light.

‘Probing this region of the electromagnetic spectrum, with the high power we’ve achieved, means we will be able to detect these gases with a high degree of sensitivity,’ said project leader Dr David Ottaway. ‘For instance, it should enable the possibility of analysing trace gases in exhaled breath in the doctors’ surgery.’

Research has shown that with various diseases, minute amounts of gases not normally exhaled can be detected in the breath; for example, acetone can be detected in the breath when someone has diabetes. Other potential applications include detection in the atmosphere of methane and ethane.

‘The main limitation to date with laser detection of these gases has been the lack of suitable light sources that can produce enough energy in this part of the spectrum,’ said Dr Ottaway. ‘The few available sources are generally expensive and bulky and, therefore, not suitable for widespread use.’

The new laser uses an optical fibre which is easier to work with, less bulky and more portable, and much more cost effective to produce than other types of laser.

The researchers, including Jesper Munch, Emeritus Professor of Experimental Physics, reported light emission at 3.6 microns, which they said is the deepest mid-infrared emission from a fibre laser operating at room temperature. They have also shown that the laser has the promise of efficient emission across a large wavelength spectrum from 3.3-3.8 microns.

‘This means it has incredible potential for scanning for a range of gases with a high level of sensitivity, with great promise as a very useful diagnostic and sensing tool,’ said Dr Ottaway.