Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared - application to trace detection of H2O2

We demonstrate the first cavity-enhanced optical frequency comb spectroscopy in the mid-infrared wavelength region and report the sensitive real-time trace detection of hydrogen peroxide in the presence of a large amount of water. The experimental apparatus is based on a mid-infrared optical parametric oscillator synchronously pumped by a high power Yb:fiber laser, a high finesse broadband cavity, and a fast-scanning Fourier transform spectrometer with autobalancing detection. The comb spectrum with a bandwidth of 200 nm centered around 3.75 {\mu}m is simultaneously coupled to the cavity and both degrees of freedom of the comb, i.e., the repetition rate and carrier envelope offset frequency, are locked to the cavity to ensure stable transmission. The autobalancing detection scheme reduces the intensity noise by a factor of 300, and a sensitivity of 5.4 {\times} 10^-9 cm^-1 Hz^-1/2 with a resolution of 800 MHz is achieved (corresponding to 6.9 {\times} 10^-11 cm^-1 Hz^-1/2 per spectral element for 6000 resolved elements). This yields a noise equivalent detection limit for hydrogen peroxide of 8 parts-per-billion (ppb); in the presence of 2.8% of water the detection limit is 130 ppb. Spectra of acetylene, methane and nitrous oxide at atmospheric pressure are also presented, and a line shape model is developed to simulate the experimental data.Comment: submitted to special FLAIR 2011 issue of Appl. Phys.

Absolute Frequency Measurement of Rubidium 5S-7S Two-Photon Transitions

We report the absolute frequency measurements of rubidium 5S-7S two-photon transitions with a cw laser digitally locked to an atomic transition and referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm) insensitive to first order in a magnetic field, is a promising candidate for frequency reference. The performed tests yield the transition frequency with accuracy better than reported previously.Comment: This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at http://dx.doi.org/10.1364/OL.38.004581. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under la

Quantum-noise-limited optical frequency comb spectroscopy

We achieve a quantum-noise-limited absorption sensitivity of 1.7/times10$^{-12}$ cm$^{-1}$ per spectral element at 400 s of acquisition time with cavity-enhanced frequency comb spectroscopy, the highest demonstrated for a comb-based technique. The system comprises a frequency comb locked to a high-finesse cavity and a fast-scanning Fourier transform spectrometer with an ultra-low-noise autobalancing detector. Spectra with a signal-to-noise ratio above 1000 and a resolution of 380 MHz are acquired within a few seconds. The measured absorption lineshapes are in excellent agreement with theoretical predictions.Comment: 18 pages, 4 figures; http://prl.aps.org/pdf/PRL/v107/i23/e23300

Fully quantum calculations of the line-shape parameters for the Hartmann-Tran profile: a CO-Ar case study

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Sensitive Fourier-transform cavity ring down spectroscopy based on a near-infrared frequency comb

International audienceMultiplexed cavity ring-down spectroscopy (CRDS) is challenging to achieve as it requires a detection scheme able to retrieve many undistorted exponential decays simultaneously [1]. We recently demonstrated Fourier transform CRDS (FT-CRDS) based on an optical frequency comb source and a time-resolved Fourier transform spectrometer (FTS) [2]. In this proof-of-concept experiment, the frequency comb was locked to a CRDS cavity using the Pound-Drever-Hall (PDH) technique, to ensure a quasi-continuous comb light transmission through the cavity. The decays were synchronized with the movement of the fast-scanning FTS, allowing to retrieve a 3D spectrum containing the untangled decays at each spectral element. The cavity was characterized by a moderate finesse of 2,000, far below standard reflectivity used for CRDS, and the comb mode absolute frequencies were not stabilized. Here, we revise the locking scheme, as depicted in Fig. 1(a): the offset frequency of the Erbium comb is stabilized to a reference radiofrequency while the repetition rate is phase-locked to a continuous wave laser emitting at 1550 nm, which in turn is locked to a cavity mode using the Pound-Drever-Hall technique

Broadband cavity ring-down Fourier-transform spectroscopy

We perform broadband cavity ring-down spectroscopy (CRDS) relying on the near-infrared frequency comb as the excitation source and a time-resolved mechanical Fourier transform spectrometer as detection device. The many decays corresponding to each spectral element are recorded simultaneously and sorted after Fourier transformation to yield the CRDS spectrum of CO in Ar contained in a 20’000-finesse cavity

Fourier transform cavity ring-down spectroscopy using an optical frequency comb source

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Fully ab initio second-overtone line shapes of carbon monoxide perturbed by argon: comparison with experiment

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