CS-LDTC16 WAVELENGTH | Alldatasheet

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© 2025 • Sales & Technical Support: (406) 587-4910 • email: sales@teamWavelength.com • web: www.teamWavelength.com Case Study CS-LDTC16 Rev. A Ultra-Sensitive CO-LITES Detection at the Parts per Quadrillion Level June, 2025 Page 1 ABSTRACT Researchers from Harbin Institute of Technology, China have developed a gas sensor for carbon monoxide (CO) using light-induced thermoelastic spectroscopy (LITES). The ultra-sensitive design enables CO detection in the parts per quadrillion (ppq) range using a multi-pass cell with a double helix pattern generated using an artificial fish swarm algorithm as well as a polymer-modified round-head quartz tuning fork with a low resonant frequency. The system achieves CO detection at concentrations as low as 23 parts per trillion (ppt) and 920.7 ppq by extending the integration time of the sensor. With a compact design, high signal-to-noise ratio, and a long gas absorption path the CO-LITES sensor provides a new standard in gas detection sensitivity for applications including semiconductor manufacturing, hydrogen fuel cells, planetary exploration, and other fields needing highly sensitive trace gas detection. SENSITIVE GAS DETECTION The ability to detect trace gases in industrial, environmental, energy, and scientific research applications can help avoid major consequences that these low concentrations of gases can cause. A highly sensitive technology can help advance semiconductor manufacturing, energy innovation, and interplanetary exploration. When producing semiconductor chips, even trace impurities within the electron gases can negatively impact the yield and reliability. When dealing with energy innovation, trace carbon monoxide (CO) by- products of fuel cells can degrade the performance of the fuel cell or cause failure. Interplanetary exploration requires sensitive sensors in the search for life and understanding planetary atmospheres and the gases they hold. 1 Whether it's energy efficiency, manufacturing, or exploration, trace gases in the parts per trillion (ppt) or even in the parts per quadrillion (ppq) could have a significant impact on safety, performance, health, or the environment. For highly sensitive measurements and detection, laser absorption spectroscopy (LAS) has gained traction among many researchers. LAS uses lasers tuned to specific gas absorption lines to detect a particular gas and to quantify the concentration of the trace gas. Because of its rapid response and high sensitivity, further developments have produced quartz-enhanced photoacoustic spectroscopy (QEPAS), advantageous due to its small size, low cost, and high Q factor. Using LAS, or some form of LAS, can provide ultra-high sensitivity gas detection for a variety of applications in the manufacturing, energy, and exploration fields. PROBLEMS AND GOALS Although QEPAS has significant advantages compared to other non-laser absorption techniques, there is a notable drawback of its design that can become problematic. In the QEPAS design, a quartz tuning fork (QTF) must be used to detect changes from the laser passing through the gas environment, detecting thermal or acoustic signals. When the QTF is submerged in acidic or corrosive gases, the QTF's surface can become damaged, affecting the sensitivity and properties of the QTF. Another issue of the design of QEPAS is the short absorption path restricting further advancement of detection capabilities. As the Beer-Lambert Law dictates, a longer path length of the light from the laser corresponds to a stronger absorption of that light from the gas through which it passes. If the gas absorption path is increased, the detection capability of the system can be improved. This is harder to achieve with the shorter path length design of QEPAS, and the exposed QTF makes the technique restrictive in its range of applications. To solve these issues, light-induced thermoelastic spectroscopy (LITES) can invert gas information from thermoelectric signals from the QTF which can change depending on the stimulation of the laser light and how much is absorbed after passing through the sample gas. This provides a non-contact method for sensitive gas detection. However, the typical two-mirror multi-pass cell (MPC) used with LITES to increase the effective optical path length can be limited in precision. Three-mirror MPCs can be used but may have complex optical structures to fully unlock the potential for ultra-sensitive gas sensors.

Figure 5. Performance of CO-LITES sensor based on optimized MPC and QTF3. a) 2f signal of the CO-LITES sensor with and human health assessment. thermal drift, changed the laser wavelength.

Case Study CS-LDTC16 Rev. A Page 5 © 2025 • Sales & Technical Support: (406) 587-4910 • email: sales@teamWavelength.com • web: www.teamWavelength.com KEYWORDS CO-LITES, quartz tuning fork, QTF, spectroscopy, carbon monoxide, CO, gas sensing, QCL, QCL driver, temperature controller, parts per quadrillion, ppq, semiconductor manufacturing, energy innovation PRODUCTS USED QCL1500 LAB, TC10 LAB

REVISION HISTORY

Document Number: CS-LDTC16 REVISION DATE NOTES A June 2025 Initial Release REFERENCES quadrillion level gas molecule detection: CO-LITES sensing. Light: Science & Applications , 14, 180 (2025). https://doi.org/10.1038/s41377-025-01864-4 USEFUL LINKS

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  • TC10 LAB Product Page PERMISSIONS Figures 1 - 6 in this case study were obtained from Reference 1. The article (Ref. 1) is distributed under terms of Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided that you give appropriate credit to the original authors and the source, provide a link to the Creative Commons license, and indicate if changes were made. Figures 1 - 3 were cropped and the captions for Figures 1 - 3 were modified. No changes were made to the other captions or images. They are presented here in their original form.