Dual-comb spectroscopy for the characterization of laboratory flames

Optical spectroscopy, in particular dual-comb (DC) spectroscopy, is a critical, non-invasive tool for combustion diagnostics, offering high precision and calibration-free advantages. However, its implementation remains challenging, especially in the mid-infrared region. This work presents the development of a robust DC spectroscopic system based on electro-optical (EO) frequency comb generators and difference frequency generation (DFG), specifically designed for the characterization of laboratory flames. Operating at a center wavelength of 3427.43 nm, the system utilizes a differential detection strategy to enable precise, calibration-free measurements of unburned methane ( CH 4 ) concentrations in a McKenna burner. The experimental results demonstrate an estimated detection limit of 1.1 ppm for a 1 m path length and effectively resolve spatial concentration gradients across the combustion region. Furthermore, the system’s high temporal resolution allowed for the identification of dynamic combustion instabilities, including self-sustained pulsations and fuel leakage under fuel-lean conditions. These findings validate the proposed EO architecture as a flexible and highly sensitive tool for advanced flame characterization. • Development of a robust mid-infrared dual-comb spectroscopy system based on electro-optical frequency combs. • Calibration-free detection of unburned methane in laboratory flames with a 1.1 ppm detection limit. • Spatially resolved measurements of methane concentration gradients in a McKenna burner. • High temporal resolution enabling the identification of combustion instabilities and fuel leakage.