Abstract
Over the last decade there has been a significant increase in the implementation of cavity ringdown- based methods for spectroscopic studies in the gas phase[l]. Although these methods have demonstrated high sensitivity in numerous applications and spectral regions, real-time applications of the approach have been hindered by the need to tune the probe laser over the absorption lineshape while the ringdown time is obtained. The resultant pointwise determination of the frequency dependent intracavity loss leads to monitoring times ranging from seconds to minutes, depending on the spectral coverage required. In many cases, large optical bandwidths need be covered in order to differential between absolute absorption intensities for the target species vs. other intracavity losses. In real-world environments, large bandwidths must frequently be measured in order to identify spectral interferences from non-target species, broadband absorption due to soot, or scattering due to particulates. As real-time environmental monitoring requires the need to deal effectively with transient conditions, tuned-frequency approaches can be inadequate.
© 2000 Optical Society of America
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