H2S and CO2 gas sensing using DFB laser diodes emitting at 1.57 μm

✍ Scribed by V. Weldon; J. O'Gorman; P. Phelan; J. Hegarty; T. Tanbun-Ek

• Book ID: 103961124
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 638 KB
• Volume: 29
• Category: Article
• ISSN: 0925-4005
• DOI: 10.1016/0925-4005(95)01669-4

✦ Synopsis

Using wavelength-modulation spectroscopy and harmonic detection, we demonstrate, for the first time, direct optical detection of H2S by probing the vt + v 2 + v 3 combination absorption band centred at a wavelength 2 = 1.59 gm using a distributed feedback (DFB) laser diode. A detection limit of less than 10 ppm at atmospheric pressure over a 5 m path length for the system is inferred from the measured detectivity at higher HzS concentrations. This detection sensitivity is at a level below the accepted 10 ppm safe-exposure limit. In addition, we demonstrate the capability of DFB laser diodes for multiple gas sensing in the 2 = 1.575 lam region with the same laser by probing the 2v~ + 2v 2 + v 3 absorption band of CO2, achieving a detection limit of about 100 ppm. These results demonstrate the utility of near-infrared laser diodes for industrial applications in the area of toxic-and trace-gas monitoring.