Abstract
A gas sensor based on quartz-enhanced photoacoustic detection and a fiber-coupled telecommunication distributed-feedback diode laser was designed and characterized for trace NH3 monitoring at a 1.53-μm wavelength (overtone absorption region). Signal and noise dependence on gas pressure were studied to optimize sensor performance. The ammonia concentration resulting in a noise-equivalent signal was found to be 0.65 parts per million by volume with 38-mW optical excitation power and a lock-in amplifier time constant of 1 s. This corresponds to a normalized absorption sensitivity of 7.2 × 10-9 cm-1 W/Hz1/2, comparable with detection sensitivity achieved in conventional photoacoustic spectroscopy. The sensor architecture can be the basis for a portable gas analyzer.
© 2004 Optical Society of America
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