High stability and fast calibration-free temperature measurement based on light-induced thermoelastic spectroscopy

Professor Ma's team at Harbin Institute of Technology has recently achieved a breakthrough in the field of gas temperature detection. For the first time, they proposed a calibration-free temperature detection method based on light-induced thermoelastic spectroscopy (LITES) technology. This technique leverages the steady-state and transient response characteristics of a quartz tuning fork (QTF) to achieve rapid and highly stable temperature measurements in complex environments, providing a new solution for combustion diagnostics. The related results, titled "High stability and fast calibration-free temperature measurement based on light-induced thermoelastic spectroscopy," were recently published in Ultrafast Science.

Accurate temperature detection in high-temperature environments such as engine combustion chambers and industrial boilers is crucial for assessing combustion efficiency and controlling pollutant emissions. However, traditional temperature measurement methods rely on intrusive probes or wall-mounted sensors, which can interfere with the combustion flow field and are not suitable for complex environments. As an emerging spectral gas sensing technology, LITES has many advantages, including strong selectivity, high sensitivity, and rapid response. However, it still faces challenges in terms of detection accuracy, stability, and response speed in practical applications. Improving the detection performance of LITES technology in complex environments and reducing the impact of environmental factors such as laser beam jitter and power fluctuations on detection results are key technical bottlenecks that need to be overcome.

To overcome the limitations of existing temperature detection technologies in complex environments, we proposed four calibration-free temperature detection methods based on LITES, as shown in Figure 2. These methods normalize the second harmonic (2f) signal with the first harmonic (1f) signal, making full use of the fundamental and overtone vibration modes of the QTF, as well as its steady-state and transient response characteristics. The specific methods are as follows: Method I (2f_fund/1f_diff), Method II (2f_fund/1f_over), Method III (2f-H_fund/1f-H_diff), and Method IV (2f-H_fund/1f-H_over). These methods can simultaneously detect 1f and 2f signals within the frequency response range of the QTF, thus achieving calibration-free temperature detection. To further enhance the sensor's signal amplitude, a novel T-shaped QTF was designed, which effectively increases energy accumulation time by reducing the fundamental and overtone frequencies, thereby improving the sensor's signal amplitude. This innovative design significantly enhances the LITES system's ability to detect temperature changes, providing solid technical support for high-precision and high-stability temperature detection.

To verify the performance of the four calibration-free temperature detection methods, the research team conducted experimental studies using a three-stage tubular furnace. The results showed that all four methods have good temperature detection capabilities, with measurement errors less than 4%. In addition, the CF-H-LITES technology based on Method IV not only performed excellently in detection performance but also reduced the measurement period to 4 s, achieving a measurement speed 5 times faster than traditional methods, indicating that CF-H-LITES technology has a faster temperature response speed. Figure 5 shows the anti-interference performance of Method IV, which effectively reduces the impact of laser beam jitter and power fluctuations on detection results by normalizing the 2f signal with the 1f signal, allowing CF-H-LITES technology to maintain high-precision detection performance in complex environments.

Conclusion and Outlook: This study proposes four new calibration-free temperature detection methods based on LITES technology, which achieve synchronous detection of first and second harmonic signals by utilizing various vibration modes and response characteristics of a single QTF, effectively reducing the impact of laser beam jitter and power fluctuations on detection results, and significantly enhancing the stability and accuracy of detection. Compared to traditional methods, this method greatly shortens the detection time and has the ability to respond quickly in extreme environments, providing important support for industrial applications that require online temperature monitoring. In addition, this method breaks through the spectral response limitations of traditional photoelectric detectors, expanding the application potential of LITES technology in full-band gas spectrum detection. The research results show great value in both theory and practical applications and have broad prospects in fields such as industrial combustion and aerospace. With the further maturation of the technology, its ability to quickly and accurately detect temperature in harsh environments will have a profound impact on related fields.

Research Team Introduction

Yufei Ma received his PhD degree in physical electronics from Harbin Institute of Technology, China, in 2013. From September 2010 to September 2011, he spent as a visiting scholar at Rice University, USA. Currently, he is a professor at Harbin Institute of Technology, China. He is the winner of National Outstanding Youth Science Fund. His research interests include optical sensors, trace gas detection, laser spectroscopy, solid-state laser and optoelectronics. He has published ~200 publications (including ~90 ESI hot/highly cited papers) and given more than 30 invited presentations at international conferences. He is the winner of 2021, 2022 and 2023 Most Cited Researchers from Elsevier.