Sensitive photoacoustic detection of ammonia with near-infrared diode lasers (1.53 μm) and a novel differential acoustic resonator is described; a sensitivity of 0.2 parts per million volume (signal-to-noise ratio = 1) is attained. To eliminate adsorption-desorption processes of the polar NH3 molecules, a relatively high gas flow of 300 SCCM was used for the ammonia-nitrogen mixture. The results are compared with recent ammonia measurements with a NIR diode and absorption spectroscopy used for detection and photoacoustic experiments performed with an infrared quantum-cascade laser. The performance of the much simpler and more compact setup introduced here was comparable with these previous state-of-the-art measurements.
© 2002 Optical Society of America
Andreas Schmohl, András Miklós, and Peter Hess, "Detection of Ammonia by Photoacoustic Spectroscopy with Semiconductor Lasers," Appl. Opt. 41, 1815-1823 (2002)