Ringdown and cavity-enhanced absorption spectroscopy using a continuous-wave tunable diode laser and a rapidly swept optical cavity

We use a rapidly swept optical cavity in a novel approach to cavity ringdow n spectroscopy (CRDS) with a continuous-wave (cw) laser. This simplifies cw -CRDS by eliminating the need for a fast optical switch and is demonstrated by recording weak combination-band spectra of carbon dioxide diluted in ni trogen, using a cw single-mode tunable diode laser (TDL) in the 1.55 mu m n ear-infrared region. We employ a simultaneous combination of CRDS and cavit y-enhanced absorption spectroscopy, to compensate for nonlinear CRDS respon se that is observed for stronger absorption features. Experimental results and performance characteristics are presented, together with numerical simu lations. (C) 2000 Published by Elsevier Science B.V. All rights reserved.