A near-infrared diode laser with sample-grating distributed Bragg reflectors was used as a widely tunable spectroscopic source for multispecies chemical sensing. Quartz-enhanced photoacoustic spectroscopy was utilized to obtain high absorption sensitivity in a compact gas cell. CO<sub>2</sub> , H<sub>2</sub>O , C<sub>2</sub>H <sub>2</sub> , and NH<sub>3</sub> were monitored. A noise equivalent sensitivity of 8×10<sup>-9</sup>cm <sup>-1</sup>W <sup>-1</sup>>Hz <sup>-1/2</sup> for NH<sub>3</sub> detection was achieved, which corresponds to a NH<sub>3</sub> mixing ratio of 4.4 parts in 10<sup>6</sup> by volume (ppmv) with a 1-s time constant and available 5.2-mW optical power in the gas cell.
© 2004 Optical Society of America
(140.5960) Lasers and laser optics : Semiconductor lasers
(280.3420) Remote sensing and sensors : Laser sensors
(300.6320) Spectroscopy : Spectroscopy, high-resolution
(300.6430) Spectroscopy : Spectroscopy, photothermal
Damien Weidmann, Anatoliy A. Kosterev, Frank K. Tittel, Neil Ryan, and David McDonald, "Application of a widely electrically tunable diode laser to chemical gas sensing with quartz-enhanced photoacoustic spectroscopy," Opt. Lett. 29, 1837-1839 (2004)