Highly Sensitive H₂S Gas Sensor Using Mid‐Infrared Interband Cascade Laser Spectroscopy With Fiber Coupling

ABSTRACT Hydrogen sulfide (H 2 S) is an extremely toxic and hazardous gas, its highly sensitive detection is of great significance for individual and environmental health protection. Weak absorption of H 2 S in near infrared (NIR) band is not conducive to the realization of high sensitivity detection. While the absorption is strong in middle infrared (MIR) band, but the lack of tail fiber output for the MIR lasers limits its application flexibility. An H 2 S gas sensor based on an infrared Interband Cascade Laser (ICL) combined with fiber coupling technique was proposed. Wavelength modulation spectroscopy (WMS) method is employed and the absorption line of H 2 S at 2639 nm is selected. The modulation amplitude is optimized for the ICL. The spatial MIR laser output by the ICL is coupled into the optical fiber and input into a gas cell. A sealed component for spatial optical‐fiber coupling is designed to avoid the absorption interference caused by air exposed to spatial light paths. The experimental results show that the sensitivity of H 2 S detection reaches 14.19 ppb and the precision is 0.75%, which is increased by 92.91% and 64.11%, respectively, comparing with the NIR detection method. The proposed sensor provides an effective solution for highly sensitive H 2 S measurement while achieving high‐precision H 2 S detection with application flexibility.