Nowadays temperature measurement plays important role in medicine, manufacturing processes, environmental control and other applications. The need for more sensitive temperature measuring devices arises, therefore, the resistance thermometers are more and more readily being replaced by the photonic temperature sensors.

Generally these sensors take advantage of the thermo-optic effect and thermal expansion caused by light. Photonic temperature sensors are attractive because they can offer much greater temperature sensitivity and more stability despite changes of mechanical or environmental origin or electromagnetic interference. Because of these appealing properties, studies of photonic temperature sensors are being carried out at an increasing pace.

Scientists from Joint Quantum Institute, University of Maryland, College Park, National Institute of Standards and Technology, Gaithersburg and Thermodynamic Metrology Group, Sensor Science Division, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, presented their study of an ultra-sensitive chip-based photonic temperature sensor. The paper was published at arXiv.org. The authors of the paper manufactured and examined a photonic sensor using silicon ring resonator structures.

Silicon ring resonators respond quickly to a small temperature shift, according to the team. This occurs due to the fact that, the refractive index and the physical dimensions of the ring change as the temperature changes. Thus, there is a temperature-induced shift in resonance wavelength of a resonator. The researchers used two types of temperature measurement modes. During the first one, the wavelength scanning mode, the temperature of the sensor was varied from 288 K to 306 K and it was found that the sensor could resolve a temperature difference of about 1 mK. The second measurement mode – the side of fringe, constant power mode – used in the same interval of temperatures proved to have a 13 times lower noise floor than the first one and, although it had a higher measurement uncertainty, it could be used in dynamic temperature measurements.

The authors of the paper claim that sensitivity ring resonators feature low noise levels and detect high temperature difference, therefore they are suitable for usage in aerospace and microfluidics. The authors also noted that the noise levels of ring resonator photonic temperature sensors will be reduced in the future thus even more improving an already impressive sensor performance.

Source: www.technology.org