A compact widely-tunable fiber-coupled sensor for trace gas detection of hydrogen sulfide (H<sub>2</sub>S) in the mid infrared is reported. The sensor is based on an external-cavity quantum cascade laser (EC-QCL) tunable between 7.6 and 8.3 mum wavelengths coupled into a single-mode hollow-core waveguide. Quartz-enhanced photoacoustic spectroscopy has been selected as detecting technique. The fiber coupling system converts the astigmatic beam exiting the laser into a TEM<sub>00</sub> mode. During a full laser scan, we observed no misalignment between the optical beam and the tuning fork, thus making our system applicable for multi-gas or broad absorber detections. The sensor has been tested on N<sub>2</sub>:H<sub>2</sub>S gas mixtures. The minimum detectable H<sub>2</sub>S concentration is 450 ppb in ~3 s integration time, which is the best value till now reported in literature for H<sub>2</sub>S optical sensors.
Widely-tunable mid-infrared fiber-coupled quartz-enhanced photoacoustic sensor for environmental monitoring.
Siciliani de Cumis M;Viciani S;Borri S;Patimisco P;Scamarcio G;De Natale P;D'Amato F;Spagnolo V
2014
Abstract
A compact widely-tunable fiber-coupled sensor for trace gas detection of hydrogen sulfide (H2S) in the mid infrared is reported. The sensor is based on an external-cavity quantum cascade laser (EC-QCL) tunable between 7.6 and 8.3 mum wavelengths coupled into a single-mode hollow-core waveguide. Quartz-enhanced photoacoustic spectroscopy has been selected as detecting technique. The fiber coupling system converts the astigmatic beam exiting the laser into a TEM00 mode. During a full laser scan, we observed no misalignment between the optical beam and the tuning fork, thus making our system applicable for multi-gas or broad absorber detections. The sensor has been tested on N2:H2S gas mixtures. The minimum detectable H2S concentration is 450 ppb in ~3 s integration time, which is the best value till now reported in literature for H2S optical sensors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
