Quantitative measurement of hydrogen sulfide gas via tunable diode laser absorption spectroscopy and integration into a lidar remote sensing

This study investigates the quantitative measurement of hydrogen sulfide (H 2 S) gas using tunable diode laser absorption spectroscopy (TDLAS) and its subsequent integration into a lidar-based remote-sensing configuration. An optimized TDLAS methodology is developed to achieve high-precision H 2 S quantification by explicitly accounting for pressure- and temperature-dependent variations in absorption line characteristics. HITRAN-based simulations are employed to guide the selection of appropriate absorption coefficients and to optimize the wavelength modulation depth under varying ambient conditions. Experimental results demonstrate accurate H 2 S concentration measurements over a dynamic range of 100–1100 ppm. The relationship between integration time and minimum detection limit (MDL) is examined, yielding a MDL of 10 ppm at 1 s integration time, which improves to 81 ppb at 100 s due to noise averaging. A degradation in sensitivity at longer integration times is observed and attributed to system-level noise sources, including laser intensity noise, optical component limitations, and photodetector noise. The developed TDLAS system is further integrated into a lidar configuration using a stable, eye-safe tunable laser diode and a calibration-free measurement approach to reduce system noise. Experimental results show good agreement with HITRAN simulations, demonstrating the reliability and versatility of the proposed approach for quantitative H 2 S measurement and its potential for lidar-based remote sensing.