We describe a portable diode-laser-based sensor for NH<sub>3</sub> detection using vibrational overtone absorption spectroscopy at 1.53 μm. Use of fiber-coupled optical elements makes such a trace gas sensor rugged and easy to align. On-line data acquisition and processing requiring <30 s can be performed with a laptop PC running LabVIEW software. The gas sensor was used primarily for NH<sub>3</sub> concentration measurements with a sensitivity of 0.7 parts per million (signal-to-noise ratio of 3) over a two-week period in a bioreactor being developed at the NASA Johnson Space Center for water treatment technologies to support long-duration space missions. The feasibility of simultaneous, real-time measurements of NH<sub>3</sub> and CO<sub>2</sub> concentrations is also reported.
© 2001 Optical Society of America
Ricardo Claps, Florian V. Englich, Darrin P. Leleux, Dirk Richter, Frank K. Tittel, and Robert F. Curl, "Ammonia Detection by use of Near-Infrared Diode-Laser-Based Overtone Spectroscopy," Appl. Opt. 40, 4387-4394 (2001)