Precise Analysis of NO₂ Concentration Based on Absorption Spectroscopy in the 6.2 µm Wavelength Region Using Multi-Voigt Fitting

A high-resolution Tunable Diode Laser Absorption Spectroscopy (TDLAS) system integrated with Multi-Voigt Fitting was developed to enable precise quantification of nitrogen dioxide (NO₂) concentrations. As a key atmospheric pollutant generated during high-temperature combustion, NO₂ requires accurate and real-time monitoring. Measurements were performed using a 1599 cm^-1 (6.25 ㎛) distributed feedback (DFB) laser over a concentration range of 10-100 ppm at both room temperature (296 K) and elevated temperature (573 K). The NO₂ absorption spectrum exhibited multiple overlapping peaks, quantitatively resolved through a Multi-Voigt Fitting algorithm. The system demonstrated high accuracy, maintaining deviations within 5% of certified reference gas concentrations across all temperature conditions. The proposed method enables high-fidelity, non-invasive NO₂ diagnostics in harsh environments and offers strong potential for deployment in combustion and environmental sensing applications.