A new type of fiber laser that can operate over a large range within the infrared light spectrum promises major advances in remote sensing of greenhouse gases.

“Most lasers work only at one wavelength of light,” says Dr. Ori Henderson-Sapir, postdoctoral fellow in physics at the University of Adelaide, where the laser was developed. “What’s special about this laser is that it not only can change wavelengths, but it can be tuned over a very large wavelength range."

Schematic diagram of the tunable fiber laser. Image credit: University of Adelaide.Schematic diagram of the tunable fiber laser. Image credit: University of Adelaide. According to project leader Associate Professor David Ottaway, from the University of Adelaide’s School of Physical Sciences and the Institute for Photonics and Advanced Sensing, the new laser operates at a wavelength where many hydrocarbon gases, including the greenhouse gases, absorb light. “This means that by changing the wavelength of our laser, we can measure the light absorption patterns of different chemicals with a high degree of sensitivity," he explains.

This functionality allows for the detection of small concentrations of such gases at considerable distances, Ottaway says. "Remote detection of greenhouse gases such as methane and ethane opens up the prospect of differentiating between various potential emission sources, such as natural gas extraction and agriculture—and so pinpoint areas of concern,” he adds.

Other potential applications for the laser include the possibility of analyzing trace gases in exhaled breath at a clinic to detect the presence of disease. Acetone, for example, can be detected in the breath when someone has diabetes.

“The main limitation to date with laser detection of these gases has been the lack of suitable and affordable light sources that can produce enough energy and operate at the correct part of the light spectrum,” says fellow researcher Stuart Jackson, associate professor of engineering at Macquarie University. The few available sources that can cover the wavelength range necessary for the detection of these gases are generally expensive and bulky and, therefore, not suitable for widespread use, he notes.

In contrast, the new laser uses an optical fiber that is comparatively easy to work with—less bulky and more portable—and significantly more cost effective to produce than other types of laser. It reaches further into the mid-infrared wavelength range than has ever been achieved before from a fiber laser operating at room temperature.

“It has incredible potential for scanning for a range of gases with a high level of sensitivity and, because of its affordability, it promises to be a very useful sensing tool,” Ottaway says. “We hope this laser will open up opportunities for lasers in the mid-infrared in a similar manner that titanium doped sapphire lasers revolutionized lasers operating in the visible and near-infrared.”

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