Laser team

Laser light waves point the way to super-accurate measurements

Scientists in Australia and Scotland have discovered a new way to use lasers for measurements, which brings a level of quantum precision never before available.

The improved sensitivity will enable the next generation of sensors with a wide variety of optical and quantum technologies.

“We have used the wave properties of light to create grainy patterns due to interference, termed ‘speckle’, which offers a sensitive probe of both the light and the environment,” says Professor Kishan Dholakia, who is jointly at the School of Biological Sciences, University of Adelaide, and the School of Physics and Astronomy, University of St Andrews.

Professor Dholakia worked with Morgan Facchin and Dr Graham Bruce from the University of St Andrews to ‘scramble’ light into a grainy pattern. They used two techniques—a piece of glass fibre the width of a human hair and a hollow sphere where the light bounces around many times before emerging.

“If you shine a laser pointer on a rough surface like a painted wall, or a piece of frosted sticky tape, the light from the laser gets scrambled into a grainy speckled pattern, said Professor Dholakia.

“If you move the laser, the exact pattern you see will change dramatically. It is this sensitivity to change that makes speckle a good choice for precision measurement.”

The technique can measure the wavelength of light at the precision of an attometre – the equivalent to measuring the length of a football pitch with an accuracy equivalent to the size of one atom.

New measuring devices made possible by the technique may have a variety of uses including in healthcare, he says.

Infection can cause changes in the refractive index of your red blood cells, which could be picked up by a sensor this sensitive.

Other potential applications are field portable sensors to detect trace gases or small concentrations of chemicals in liquids.