Doppler-free nonlinear absorption in ethylene by use of continuous-wave cavity ringdown spectroscopy

Bucher, Christine R.; Lehmann, Kevin K.; Plusquellic, David F.; Fraser, Gerald T.

doi:10.1364/ao.39.003154

Cited by 45 publications

(31 citation statements)

References 29 publications

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“…Many cavityenhanced spectroscopies exhibit significant sensitivity and potential 5,6 , but their scanning rates are limited by reliance on either mechanical or thermal frequency tuning 7 . Here, we present frequency-agile, rapid scanning spectroscopy (FARS) in which a high-bandwidth electro-optic modulator steps a selected laser sideband to successive optical cavity modes.…”

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confidence: 99%

“…This technique, which we refer to as frequency-agile, rapid scanning (FARS) cavity ring-down spectroscopy, allows for ultrasensitive measurements in which the acquisition rate is limited only by the cavity response. Unlike earlier techniques [8][9][10][11]18,19 , FARS allows for spectra to be recorded without any dead time due to scanning of the laser frequency, offers a metrology-level frequency axis and utilizes a conventional Fabry-Pérot resonator rather than more unusual and cumbersome cavity configurations.This frequency stepping of the probe laser is enabled by the use of a microwave driver and a high-bandwidth electro-optic modulator (EOM) to generate a series of sidebands on the probe laser (Fig. 1).…”

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“…Because of their sensitivity, continuous-wave (c.w.) cavity-enhanced spectroscopies have significant potential for addressing these challenging applications 6,14,15 . However, the low mechanical or thermal tuning rates of c.w.…”

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Frequency-agile, rapid scanning spectroscopy

et al. 2013

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Challenging applications in trace gas measurements require low uncertainty and high acquisition rates [1][2][3][4] . Many cavityenhanced spectroscopies exhibit significant sensitivity and potential 5,6 , but their scanning rates are limited by reliance on either mechanical or thermal frequency tuning 7 . Here, we present frequency-agile, rapid scanning spectroscopy (FARS) in which a high-bandwidth electro-optic modulator steps a selected laser sideband to successive optical cavity modes. This approach involves no mechanical motion and allows for a scanning rate of 8 kHz per cavity mode, a rate that is limited only by the cavity response time itself. Unlike rapidly frequency-swept techniques 8-11 , FARS does not reduce the measurement duty cycle, degrade the spectrum's frequency axis or require an unusual cavity configuration. FARS allows for a sensitivity of ∼2 3 10 212 cm 21 Hz 21/2 and a tuning range exceeding 70 GHz. This technique shows promise for fast and sensitive trace gas measurements and studies of chemical kinetics.A multitude of applications have emerged that require rapid sensing of trace gas species, encompassing areas as varied as greenhouse gas monitoring 1,4,12 , breath analysis 2,13 , explosive detection 3 and chemical process monitoring. Because of their sensitivity, continuous-wave (c.w.) cavity-enhanced spectroscopies have significant potential for addressing these challenging applications 6,14,15 . However, the low mechanical or thermal tuning rates of c.w. lasers have generally limited the use of these techniques to static or slowly varying analytes. Attempts to alleviate this limitation have relied on sweeping the laser frequency [8][9][10][11] , which can compromise the fidelity of the spectrum and the instrument sensitivity 16 and reduce the measurement duty cycle. We present a new approach for cavity ring-down spectroscopy 17 in which the laser frequency is rapidly stepped to successive resonances through the use of highbandwidth electro-optics. This technique, which we refer to as frequency-agile, rapid scanning (FARS) cavity ring-down spectroscopy, allows for ultrasensitive measurements in which the acquisition rate is limited only by the cavity response. Unlike earlier techniques [8][9][10][11]18,19 , FARS allows for spectra to be recorded without any dead time due to scanning of the laser frequency, offers a metrology-level frequency axis and utilizes a conventional Fabry-Pérot resonator rather than more unusual and cumbersome cavity configurations.This frequency stepping of the probe laser is enabled by the use of a microwave driver and a high-bandwidth electro-optic modulator (EOM) to generate a series of sidebands on the probe laser (Fig. 1). We then use the cavity as a spectral filter such that only a single, selected sideband is resonant. Thus, we are able to transfer the superior switching bandwidth and precision of microwave sources into the optical domain. Ring-downs are then initiated by simply switching off the microwave frequency, thus removing the need for an acousto-...

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Frequency-agile, rapid scanning spectroscopy

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“…Intensity-dependent decay rates have recently been observed in CRD. 34,35 In this paper laser bandwidth effects have not been discussed. Indeed, for the case in which the bandwidth of the laser source exceeds the widths of molecular resonances the decay transients will exhibit multiexponential decay.…”

Section: Discussionmentioning

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

et al. 2001

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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.

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“…In some CW CRD experiments, nonlinear effects were observed and discussed in two specific regimes. When the ring-down time is much shorter than the population relaxation time, absorption losses keep constant at the saturated value existing at the CRD start time, and the decay will be simply exponential [18]. In the opposite regime (the so-called adiabatic approximation), the saturation level of the optical transitions reaches the steady state at each point of the ringdown profile [19].…”

Section: Introductionmentioning

confidence: 99%

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

Giusfredi¹,

Galli²,

Mazzotti³

et al. 2015

J. Opt. Soc. Am. B

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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.

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Doppler-free nonlinear absorption in ethylene by use of continuous-wave cavity ringdown spectroscopy

Cited by 45 publications

References 29 publications

Frequency-agile, rapid scanning spectroscopy

Frequency-agile, rapid scanning spectroscopy

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

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

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