Introduction to Cavity Enhanced Absorption Spectroscopy

Romanini, D.; Ventrillard, I.; Méjean, G.; Morville, Jérôme; Kerstel, Erik

doi:10.1007/978-3-642-40003-2_1

Cited by 63 publications

(55 citation statements)

References 194 publications

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“…(1) Δ I/I is the root-mean-square value of the relative intensity noise over a given measurement time and L eff is the effective interaction length. Under weak absorption conditions this is in turn proportional to the geometrical length L and to the finesse F of the cavity, by the relation L eff = 2∙ L∙F /π41. Increasing F and L is thus beneficial for the sensitivity of the spectrometer provided that the intensity noise term is preserved.…”

Section: Resultsmentioning

confidence: 99%

Comb-locked Lamb-dip spectrometer

Gatti

Gotti

Alessio

et al. 2016

Sci Rep

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Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10−11 cm−1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10−23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

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Section: Resultsmentioning

confidence: 99%

Comb-locked Lamb-dip spectrometer

Gatti

Gotti

Alessio

et al. 2016

Sci Rep

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“…The effective path length L ( λ ) is set by the optical losses within the cavity (mirror transmission, scattering, absorption) and is parameterized by the finesse, ℱ( λ ) = π /(losses( λ )): L ( λ ) varies between ℱ( λ )/ π to 2ℱ( λ )/ π depending on the configuration [158, 159]. Spectroscopy systems use either the fundamental spatial mode, particularly if used with a spatially coherent source, or multiple spatial modes of the cavity, particularly if used with a spatially incoherent source.…”

Section: Techniquesmentioning

confidence: 99%

Gas-phase broadband spectroscopy using active sources: progress, status, and applications [Invited]

et al. 2016

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Broadband spectroscopy is an invaluable tool for measuring multiple gas-phase species simultaneously. In this work we review basic techniques, implementations, and current applications for broadband spectroscopy. We discuss components of broad-band spectroscopy including light sources, absorption cells, and detection methods and then discuss specific combinations of these components in commonly-used techniques. We finish this review by discussing potential future advances in techniques and applications of broad-band spectroscopy.

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“…For a given set of thermodynamic conditions and a particular molecular absorption transition, the BeerLambert law for absorption spectroscopy provides only one option for maximizing the measured laser absorption signal, which is to increase the beam path length within the probe gas volume [3]. Optically resonant cavities are the most efficient means of achieving manifold increase in effective path length and, hence, the sensitivity of an existing laser absorption diagnostic [4].…”

Section: Introductionmentioning

confidence: 99%

Intra-pulse laser absorption sensor with cavity enhancement for oxidation experiments in a rapid compression machine

Nasir

Farooq

2018

Opt. Express

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Abstract:A sensor based on a mid-IR pulsed quantum cascade laser (QCL) and off-axis cavity enhanced absorption spectroscopy (OA-CEAS) has been developed for highly sensitive concentration measurements of carbon monoxide (CO) in a rapid compression machine. The duty cycle and the pulse repetition rate of the laser were optimized for increased tuning range, high chirp rate, and small line width to achieve effective laser-cavity coupling. This enabled spectrally resolved CO line-shape measurements at high pressures (P ~10 bar). A gain factor of 133 and a time resolution of 10 μs were demonstrated. CO concentration-time profiles during the oxidation of highly dilute n-octane/air mixtures were recorded, illustrating new opportunities in RCM experiments for chemical kinetics. 223-232 (2015). 16. R. M. Spearrin, C. S. Goldenstein, J. B. Jeffries, and R. K. Hanson, "Quantum cascade laser absorption sensor for carbon monoxide in high-pressure gases using wavelength modulation spectroscopy," Appl. Opt. 53(9), 1938-1946 (2014

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Introduction to Cavity Enhanced Absorption Spectroscopy

Cited by 63 publications

References 194 publications

Comb-locked Lamb-dip spectrometer

Comb-locked Lamb-dip spectrometer

Gas-phase broadband spectroscopy using active sources: progress, status, and applications [Invited]

Intra-pulse laser absorption sensor with cavity enhancement for oxidation experiments in a rapid compression machine

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