Detecting toxic or flammable gases in industrial settings like mines, or oil and gas refineries, can be a matter of life and death. Currently portable detectors that are commonly used are electrochemical-based, with a chemical reaction occurring between the gas and a thin metallic film in the detector.
Photonic Innovations, a spin-out company from the University of Otago, is commercialising a gas detector which uses laser spectroscopy. The technology was initially developed by Andrew Wilson and relies on the fact that each gas has a unique “signature” that can be detected in the beam of a laser.
Ruth Beran meets Photonic Innovations CEO Ojas Mahapatra (above right) and researcher Gavin King (above left) to see the initial prototype, and a smaller version which has been developed to detect ammonia gas. One of the novel parts to the detector is the optical cavity which reduces the path length of the laser bean required to detect the gas.
“What we’re looking at is ammonia gas, and it’s only very weakly absorbing. To get any sort of accuracy you need a path length that is many, many metres long, and makes it hard to build things,” says researcher Gavin King. “So what we do is have an optical cavity: two mirrors set up opposing each other that bounce the light back and forth between them so it comes out and hits a detector, which is then run into the computer and processed to figure out the concentration.”