UK scientists beat crystal maze
19 Oct 2011 by Evoluted New Media
Birefringent crystals can be calibrated and used as highly accurate temperature gauges, but their ability to measure temperature is compromised by changes in the thickness and orientation of the crystal.However, researchers from the Universities of Warwick and Oxford have developed a form of birefringent crystal that can deliver highly accurate temperature readings down to individual millikelvins.
Birefringent crystals split light passing through it into two separate rays, with the size of the effect altering in proportion to the temperature of the crystal. However, changes in the thickness and orientation of the crystal affect its ability to do this accurately.
Researchers have modified the properties of crystalline lithium tantalite so that its birefringence is virtually independent of the crystals thickness and position, making it resistant to vibration and cheaper to manufacture.
“This advance allows us to create a new generation of robust reliable birefringent crystal based temperature sensing equipment which will be particularly valuable in electromagnetic radio frequency and high voltage environments, where other types of sensor are subject to large errors due to interference,” said Professor Pam Thomas from Warwick.
The team have made the birefringence of the crystal almost zero in magnitude in all directions – the material is close to being optically isotropic like ordinary glass. However, the slightest temperature change induces a rapid splitting of light, making it a reliable, robust and very sensitive method for measuring temperature.
“This opens up new possibilities for remote temperature sensing of challenging environments,” said Professor Mike Glazer, from Oxford. “As the birefringence changes detection in these crystals can actually be operated remotely as only the crystal itself needs to be in the environment.”
The team have named their device the Zero-Birefringence Optical Temperature Sensor or Z-BotS. They are seeking follow-on funding to develop it from a bench –top proof-of-concept to a miniaturised commercially-viable package.
