Differential cavity ring-down spectroscopy

Abstract

High-precision cavity-enhanced spectroscopic measurements are commonly compromised by interferences caused by external etalons. Here, we present the differential cavity ring-down spectroscopy (D-CRDS) technique for reducing these perturbations. We discuss how etalons are caused by coupled-cavity interactions between the primary ring-down cavity and other optical elements of the experiment, and we model and experimentally verify how drift in cavity base loss correlates with barometric pressure and laboratory temperature. D-CRDS measurements of near-infrared ${\mathrm{CO}}_2$ spectra that are insensitive to etalon-induced distortions are then presented. Based on an average of $\sim 100$ spectra, these results yield a signal-to-noise ratio of $170,000:1$ and a minimum detectable absorption coefficient of $4\times {10}^{-12}{\mathrm{cm}}^{-1}$.

© 2013 Optical Society of America

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