Sulfur dioxide sensing based on external cavity quantum cascade lasers

• Main Author: Sun, Jingru
• Other Authors: Wang Qijie
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Engineering; External cavity quantum cascade laser (EC-QCL); Sulfur dioxide (SO2) detection; Mid-infrared absorption spectroscopy; Gas monitoring; Detection limit
• Online Access: https://hdl.handle.net/10356/182923
• Institution: Nanyang Technological University

This thesis focuses on sulfur dioxide (SO2) gas detection methods utilizing ex- ternal cavity quantum cascade laser (EC-QCL) technology. SO2 is a significant air pollutant that has substantial impacts on both human health and the envi- ronment, making accurate and sensitive detection of SO2 concentrations crucial. The paper begins with a review of traditional SO2 detection methods, including chemical analytical techniques, electrochemical sensors, non-dispersive infrared spectroscopy (NDIR), and ultraviolet differential absorption spectroscopy (UV- DOAS). Following this, the principle of mid-infrared gas detection using QCLs is introduced, along with the distinct advantages of EC-QCLs. In the experi- mental section, a detection system based on EC-QCL was developed, and the absorption spectrum of SO2 was measured in the mid-infrared range. Finally, the experimental results demonstrate that the EC-QCL operates stably in single- mode, showing a strong linear relationship between SO2 concentration and ab- sorbance, which confirms the high sensitivity and low detection limit of the system. This study presents an effective solution for real-time SO2 monitoring, with promising applications in environmental and industrial contexts.