A novel technique to measure trace gas concentrations is reported. It is based on a high finesse Fabry-Perot cavity, used as a gas cell, thus providing very long interaction path- lengths. As in Cavity-Ring-Down Spectroscopy, light absorption inside the cavity is detected, but measurements are performed in the frequency domain instead of the commonly used time domain. Moreover, wavelength modulation spectroscopy is performed for sensitive detection of absorption losses. Monitoring of water vapor near 1400 nm is demonstrated using this method.

Date Published: 16 September 1999
PDF: 4 pages
Proc. SPIE 3821, Environmental Sensing and Applications, (16 September 1999); doi: 10.1117/12.364169

Published in SPIE Proceedings Vol. 3821:
Environmental Sensing and Applications
Michel R. Carleer; Moira Hilton; Torsten Lamp; Rainer Reuter; George M. Russwurm; Klaus Schaefer; Konradin Weber; Klaus C. H. Weitkamp; Jean-Pierre Wolf; Ljuba Woppowa, Editor(s)