Smelling With a Laser

Principle of a laser comb measuring the light absorption patterns of carbon dioxide molecules. (Source: S. Scholten)

University of Ade­laide researchers have created a laser that can “smell” different gases within a sample. Appli­cations for the new device lie not just in environ­mental monitoring and detecting industrial conta­mination, but may eventually be used to diagnose disease by smelling the breath. The researchers liken the ability of the laser to differen­tiate between different gas compounds in a sample to the sensi­tive nose of a blood­hound. But rather than smell, the device uses patterns of light absorp­tion to measure the compo­sition of the sample.

From the Univer­sity’s Institute for Photonics and Advanced Sensing IPAS, the researchers developed a method to measure with a laser the amount of carbon dioxide in a gas sample in under one second, with high accu­racy and preci­sion. “The ability to rapidly measure gas compo­sition to such high accuracy is cutting edge,” says Sarah Scholten, PhD candidate in the University’s School of Physical Sciences. “With further develop­ment, it opens the way for real-time and inex­pensive moni­toring and analysis that can be carried out in the field, or in the doctor’s surgery, by non-specia­list operators.”

The device exploits a Nobel-prize winning tech­nology of optical frequency comb, developed by US and German scientists. This laser comb gene­rates millions of different light frequen­cies or colours at once. The researchers pass this special light through a sample of gas where each gas molecule absorbs a distinc­tive set of colours. The pattern of light absorp­tion is a unique finger­print of the gas compo­sition of the sample.

“This first work aims at atmo­spheric monitoring, however, the technique is broadly appli­cable and offers an avenue for near-universal concen­tration measure­ments,” says Chris Perrella, post­doctoral fellow. The group now aims to use the laser comb to unravel the chemical compo­sition of the exhaled breath – in this much more complex situa­tion they hope to find tell-tale chemical signs that point to under­lying disease. The ulti­mate goal is to use the laser as a screening tool to discover a serious illness even before the patient is aware of the condi­tion. (Source: Univ. of Adelaide)

Reference: S. K. Scholten et al.: Number-Density Measurements of CO2 in Real Time with an Optical Frequency Comb for High Accuracy and Precision, Phys. Rev. Appl. 9, 054043 (2018); DOI: 10.1103/PhysRevApplied.9.054043

Link: Institute for Photonics and Advanced Sensing, School of Physical Sciences, The University of Adelaide, Adelaide, Australia

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