Theory of saturated-absorption cavity ring-down: radiocarbon dioxide detection, a case study

Abstract

The theoretical bases of saturated-absorption cavity ring-down (SCAR) spectroscopy are treated and described in detail in different transition broadening regimes. All the approximations that are introduced to achieve a model as simple and accurate as possible are discussed. In the Voigt broadening regime, a calibration factor that relates the measured spectral areas in the saturated and linear absorption regimes is retrieved. A relevant application of this technique to the measurement of radiocarbon dioxide concentration at both enriched and natural abundance (∼10 −12 ) is presented. The population relaxation rate of one ro-vibrational state of the ν 3 band is measured for this highly diluted CO 2 isotopologue.

Precision interferometric measurements of mirror birefringence in high-finesse optical resonators

“…Among possible sources of non-exponential behavior, some common examples include interference from higher-order transverse modes [24] and saturation of the intracavity absorption [25–28]. Perturbed cavity decays can also originate from small intrinsic birefringence found in all real supermirror coatings.…”

Optical Measurement of Radiocarbon below Unity Fraction Modern by Linear Absorption Spectroscopy

“…The relative frequencies of all interfering transitions from 12 C 16 O 2 , 13 C 16 O 2 , and 14 N 2 16 O were fixed to known literature values. 10,22,30 In addition to the target 14 C 16 O 2 transition, we included in our model two nearby overlapping 13 C 16 O 2 transitions (labeled in Fig. 2), one nearby 14 N 2 16 O transition (labeled in Fig.…”

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

“…The degree of saturation can be estimated from the recorded line profile using (5). The saturated absorption − 0 of a homogeneously broadened transition in a collimated Gaussian beam is described by [43]:…”

“…p = 500 mbar are strongly influenced by saturation and correspond to 5.2% and 18%, respectively, of the calculated nonsaturated signal. Assuming an effective two-level model for CO analogous to [43], the population ρ A of the vibrational ground state can be estimated (compare (32) in [43]). For I sat (500 mbar) = 4.78 W mm −2 and I 0 = 73 W mm −2 , ρ A in the center of the beam (r = 0) and at r = σ 0 is depleted to 53% and 66%, respectively, of its equilibrium value, close to the fully depleted value of 50%.…”