Nonlinear effects in pulsed cavity ringdown spectroscopy of lithium vapour

Temperature-scanning saturation cavity ring-down spectrometry for Doppler-free spectroscopy

Saturation cavity ring-down spectroscopy (SCRDS) is a powerful Doppler-free spectroscopy means for measuring absolute frequencies of transitions at the ultra-low uncertainties. We report in this paper a simple way to implement it by temperature scanning the cavity length, which circumvents the need for a complex optical cavity-length stabilization system based upon a piezoelectric actuator (PZT). To demonstrate this approach, the absolute frequencies of the two transitions, R6F1 of the 2v₃ and Q9A1 of the 2v₂ + v₃ bands, of ¹²CH₄, are determined to be 182 185 269.362(20) MHz and 182 187 617.543(39) MHz. The accuracy of measurements is improved by about 3-4 orders of magnitude when compared to those obtained with conventional spectroscopic methods.

Saturation dynamics and working limits of saturated absorption cavity ringdown spectroscopy

The decay transient dynamics and the optimum experimental conditions for reliable gas absorption measurements have been investigated using saturated CRDS (Sat-CRDS, SCAR).

Saturated-absorption cavity ring-down spectroscopy

We report on a novel approach to cavity ring-down spectroscopy with the sample gas in saturated-absorption regime. This technique allows us to decouple and simultaneously retrieve the empty-cavity background and absorption signal, by means of a theoretical model that we developed and tested. The high sensitivity and frequency precision for spectroscopic applications are exploited to measure, for the first time, the hyperfine structure of an excited vibrational state of 17O12C16O in natural abundance with an accuracy of a few parts in 10{-11}.

Quantitative analysis of decay transients applied to a multimode pulsed cavity ringdown experiment

The intensity and noise properties of decay transients obtained in a generic pulsed cavity ringdown experiment are analyzed experimentally and theoretically. A weighted nonlinear least-squares analysis of digitized decay transients is shown that avoids baseline offset effects that induce systematic deviations in the estimation of decay rates. As follows from simulations not only is it a method that provides correct estimates for the values of the fit parameters, but moreover it also yields a correct estimate of the precision of the fit parameters. It is shown experimentally that a properly aligned stable optical resonator can effectively yield monoexponential decays under multimode excitation. An on-line method has been developed, based on a statistical analysis of the noise properties of the decay transients, to align a stable resonator toward this monoexponential decay.