Abstract
Concise open-path continuous-wave cavity ring-down spectroscopy (CW-CRDS) with a bow-tie cavity structure is demonstrated in the single- and dual-optical-path experiments for multicomponent gas detection, e.g., greenhouse gas concentration evaluation in ambient air. Owing to its features of optical feedback suppression and small free spectral range (FSR), the bow-tie configuration shows its special advantages in the realization of both a compact arrangement and two counter-propagating non-interference optical paths. The minimum of the Allan deviation reaches for an integration time of 100 s, corresponding to the noise equivalent absorption coefficient of . The detection sensitivity of methane is deduced to be 0.9 ppbv with its absorption cross section of in the 512 decays averaging mode. A wavelength-correction method is proposed to reduce by about 30% the uncertainty in the measurements caused by the deviation in the wavelength resonance between incident laser and ring-down cavity. The concentrations of greenhouse gases in ambient air are measured by the open-path CW-CRDS with the uncertainties of 0.02, 100, and 10 ppmv for , , and , respectively.
© 2019 Optical Society of America
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