Abstract
There is increasing industrial demand, particularly within the clean room community, for rapid online measurement of a number of airborne molecular contaminants. These measurements are usually made with commercially available cavity ring-down spectrometers, but more recently developed techniques offer potentially better sensitivity and more rapid sampling. In this paper we present ammonia spectroscopy data from a newly developed noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) system at 1532 nm, which is designed to be transportable and operate in an industrial environment. We demonstrate this using an optical cavity of 9 kHz fringe width ( free spectral range and finesse of 169,000) and a distributed-feedback diode laser with a relatively broad free-running linewidth. The variation in NICE-OHMS ammonia signal amplitude is presented at different concentrations in one atmosphere of nitrogen, generated from traceable reference standards, with a flow rate of 1–2 l/min. We derive a calibration curve for our device for concentrations in the range from 100 nmol/mol to 10 μmol/mol.
© 2017 Optical Society of America
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