title: Optoacoustic trace-gas monitoring with near-infrared diode lasers.
abstract: An inexpensive resonant optoacoustic monitoring system using near-infrared laser diodes was developed. It was demonstrated that wavelength modulation at the resonance frequency of the cell provides a superior signal-to-noise ratio compared with amplitude modulation and eliminates background drifts and fluctuations. The system was tested out on ammonia. Its sensitivity is 8 parts in 10(9) (S/N = 1) at atmospheric pressure, which corresponds to a minimum detectable absorption coefficient of approximately 3.5 × 10(-11) cm(-1) W(-1). The pressure dependence of the optoacoustic resonance was also investigated. The monitor can be used as a continuous flow-through system up to a flow rate of approximately 3.5 L/min.
authors.forename: M
authors.initials: M
authors.lastname: Fehér
authors.forename: Y
authors.initials: Y
authors.lastname: Jiang
authors.forename: J P
authors.initials: JP
authors.lastname: Maier
authors.forename: A
authors.initials: A
authors.lastname: Miklós