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World's most sensitive thermometer made from light


June 3, 2014

Thermometer made of light is claimed accurate to 30 billionths of a degree  (Image: Dr. James Anstie, University of Adelaide)

Thermometer made of light is claimed accurate to 30 billionths of a degree (Image: Dr. James Anstie, University of Adelaide)

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By exploiting the difference between the speed of two different beams of colored light when traveling through a heated crystalline disk, University of Adelaide researchers claim to have produced the world's most sensitive thermometer – with an accuracy of 30 billionths of a degree.

The thermometer works by using a laser to inject red and green light into a highly polished crystalline disk. As the refractive index (basically, how much the light is bent) of the crystal is dependent upon the ambient temperature, the two colors travel at slightly different speeds in the crystal and the researchers are able to measure that minute speed difference and extrapolate a very accurate temperature reading.

"By forcing the light to circulate thousands of times around the edge of this disk in the same way that sound concentrates and reinforces itself in a curve in a phenomena known as a 'whispering gallery' – as seen in St Paul's Cathedral in London – we can measure this minuscule difference in speed with great precision," said Professor Andre Luiten, Chair of Experimental Physics in IPAS and the School of Chemistry and Physics.

A "whispering gallery" is usually a circular or hemispherical structure where whispered acoustic communication is possible from any part of the internal circumference to any other part because waves form on the walls to carry the sound around. This phenomenon also exists for light, so the University of Adelaide team has taken advantage of this resonance to concentrate the beams around a disk.

Claimed to be three times more precise than any other thermometer currently available, the researchers from the school’s Institute for Photonics and Advanced Sensing (IPAS) are hopeful that the new technique could be redesigned to take a myriad other ultra-sensitive measurements including pressure, humidity, force, or looking for a specific chemical.

"Being able to measure many different aspects of our environment with such a high degree of precision, using instruments small enough to carry around, has the capacity to revolutionize technologies used for a variety of industrial and medical applications where detection of trace amounts has great importance," Professor Luiten added.

According to the team, it was also able to control active suppression of temperature fluctuations in the system by controlling the intensity of the driving laser to further enhance the accuracy of the temperature readings.

The research has been published in the journal Physical Review Letters.

Source: University of Adelaide

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf. All articles by Colin Jeffrey
1 Comment

Colin, this is lazy journalism. In the headline, you correctly (though unscientifically) described this thermometer as the world's most sensitive one. Then in the body of your article, you incorrectly call it the most accurate, but, as if to have a bet each way, you also call it the most precise. You use the words "accurate" and "precise" (and their noun forms) as if they mean the same thing. Anyone who did high school science should know they are not. (If you're not sure of the difference, you can learn about it on Youtube.)

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