In-situ trace gas analysis using high-frequency modulation spectroscopy with tunable diode lasers
Authors: Werle Peter W., Muecke Robert J.
Autors Affiliation: Fraunhofer Inst. fuer Atmospharische, Umweltforschung,, Garmisch-Partenkirchen, Ger, Germany
Abstract: The main requirements for in situ trace gas analysis, process and air pollution monitoring are specificity, high time resolution, and high sensitivity. Tunable diode lasers absorption spectroscopy is increasingly being used to measure trace gas concentrations down to low ppbv-levels (10 -9 volume mixing ratio). The applications of high frequency modulation (FM) schemes can further improve sensitivity and detection speed of modern instrumentation. In this paper the FM technique will be reviewed with respect to current limitations of tunable diode laser spectroscopy. Recent investigations and findings will be described with emphasis on the work done in our laboratory and novel approaches will be discussed. Some applications related to quality control and ISO calibration as well as fast and high sensitivity measurement challenges will be discussed.
KeyWords: Frequency modulation spectroscopy; Trace gas analysis, Absorption spectroscopy; Air pollution; Frequency modulation; Laser tuning; Monitoring; Quality control; Semiconductor diodes; Semiconductor lasers; Trace analysis, GasesDOI: 10.1117/12.221075