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19th International Conference on Photoacoustic and Photothermal Phenomena (ICPPP) -- JUL 16-20, 2017 -- Bilbao, SPAIN Kaya, Necati/0000-0001-9461-7623 WOS: 000431762900001 We have developed a novel optical setup which is based on a high finesse cavity and absorption laser spectroscopy in the near-IR spectral region. In pilot experiments, spectrally resolved absorption measurements of biomarkers in exhaled breath, such as methane and acetone, were carried out using cavity ring-down spectroscopy (CRDS). With a 172-cm-long cavity, an efficient optical path of similar to 132 km was achieved. The CRDS technique is well suited for such measurements due to its high sensitivity and good spectral resolution. The detection limits for methane of similar to 8 ppbv and acetone of similar to 2.1 ppbv with spectral sampling of 0.005 cm(-1) were achieved, which allowed to analyze multicomponent gas mixtures and to observe absorption peaks of (CH4)-C-12 and (CH4)-C-13. Further improvements of the technique have the potential to realize diagnostics of health conditions based on a multicomponent analysis of breath samples. Robert A. Welch FoundationThe Welch Foundation [A1546]; Qatar Foundation [NPRP 8-735-1-154]; Turkish Ministry of EducationTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK); Higher Committee for Educational Development in Iraq (HCED) This work was supported by the Robert A. Welch Foundation Grant No. A1546 and the Qatar Foundation under the Grant NPRP 8-735-1-154. AB thanks for the support of the Turkish Ministry of Education, and EA thanks for the support of the Higher Committee for Educational Development in Iraq (HCED).

We developed a mid-infrared dual frequency comb spectrometer with a mulitpass cell of ~580 m effective length for acetone detection. The detection limit is ~ 2 ppmv under ambient air condition with 80 ms acquisition time.

We employed a midinfrared frequency comb source for methane detection in ambient air. The transmitted spectra over a bandwidth of about 500 nm were recorded with an optical spectrum analyzer under various experimental conditions of different path lengths. The normalized absorption spectra were compared and fitted with simulations, yielding quantitative values of concentrations of methane and water vapor in the ambient air. The 3σ detection limit was ∼6.6×10−7 cm−1 in ambient air for a broad spectral range, achieved with a path length of ∼590 m. This approach provides a broad spectral range, a large dynamic range, high sensitivity, and accurate calibration. The performed analysis of the residuals shows that an excellent agreement between the measured and calculated spectral profiles was obtained.

We present a femtosecond frequency comb vernier spectrometer in the near infrared with a femtosecond Er doped fiber laser, a scanning high-finesse cavity and an InGaAs camera. By utilizing the properties of a frequency comb and a scanning high-finesse cavity such a spectrometer provides broad spectral bandwidth, high spectral resolution, and high detection sensitivity on a short time scale. We achieved an absorption sensitivity of ~8 × 10(-8) cm(-1)Hz(-1/2), corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency range of ~5 THz. Such measurements have broad applications for sensing greenhouse gases in this fingerprint near infrared region with a simple apparatus.

We utilize mid-infrared dual frequency comb spectroscopy for the detection of methane in ambient air. Two mid-infrared frequency comb sources based on femtosecond Er:fiber oscillators are produced through difference frequency generation with periodically poled MgO-doped lithium niobate crystals and stabilized at slightly different repetition rates at about 250 MHz. We performed dual frequency comb spectroscopy in the spectral range between 2900 cm−1 and 3150 cm−1 with 0.07 cm−1 resolution using a multipass cell of ~580 m path length, and achieved the sensitivity about 7.6 × 10−7 cm−1 with 80 ms data acquisition time. We determined the methane concentration as ~1.5 ppmv in the ambient air of the laboratory, and the detection limit as ~60 ppbv for the current setup.

We exploited a mid-infrared frequency comb source as a high brightness laser source for trace gas detection in air with different path lengths. The MIR frequency comb source (Menlo Systems, Mid-IR Comb) was based on difference frequency generation with fiber lasers [1]. We employed flip mirrors to reroute the mid-infrared beam for different path lengths, including a homebuilt multipass cell of ∼584 m path length and open air paths of up to ∼40 m. The transmission spectra were recorded with an optical spectrum analyser (Yokogawa, AQ6376).