Abstract

Application of direct absorption techniques is advantageous in a variety of research fields since quantitative absolute concentration data as well as absolute frequency de pendent absorption cross-sections can be extracted from the measurements. Over the last few years it has been demonstrated that Cavity Ring Down (CRD) spectroscopy is a powerful method to perform direct absorption measurements with pulsed light sources. In the CRD detection scheme the rate of absorption rather than the magnitude of absorption of a light pulse coupled into a high-Q optical cavity is measured. The advantage over normal absorption spectroscopy results from (i) the intrinsic in sensitivity of the CRD technique to light source intensity fluctuations, and (ii) the extremely long effective path-lengths (many kilometers) that can be realized in stable optical cavities.

© 1998 IEEE