Widely-tunable mid-infrared fiber-coupled quartz-enhanced photoacoustic sensor for environmental monitoring.
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 μm 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(00) 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.
M
M
Siciliani de Cumis
S
S
Viciani
S
S
Borri
P
P
Patimisco
A
A
Sampaolo
G
G
Scamarcio
P
P
De Natale
F
F
D'Amato
V
V
Spagnolo
D004784:Environmental Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D005740:Gases / Q000032:analysis*; D054023:Lasers, Semiconductor; D011791:Quartz; D013057:Spectrum Analysis / Q000295:instrumentation*
D005740:Gases; D011791:Quartz