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| 2. |
- Axner, Ove, 1957-, et al.
(författare)
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NICE-OHMS – frequency modulation cavity-enhanced spectroscopy : principles and performance
- 2014
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Ingår i: Cavity-Enhanced Spectroscopy and Sensing. - Berlin : Springer Berlin/Heidelberg. - 9783642400025 - 9783642400032 ; , s. 221-251
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Bokkapitel (refereegranskat)abstract
- Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a sensitive technique for detection of molecular species in gas phase. It is based on a combination of frequency modulation for reduction of noise and cavity enhancement for prolongation of the interaction length between the light and a sample. It is capable of both Doppler-broadened and sub-Doppler detection with absorption sensitivity down to the 10−12 and 10−14 Hz−1/2 cm−1 range, respectively. This chapter provides a thorough description of the basic principles and the performance of the technique.
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| 3. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry incorporating an optical circulator
- 2014
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 39:2, s. 279-282
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Tidskriftsartikel (refereegranskat)abstract
- To reduce the complexity of fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry, a system incorporating a fiber-coupled optical circulator to deflect the cavity-reflected light for laser stabilization has been realized. Detection near the shot-noise limit has been demonstrated for both Doppler-broadened and sub-Doppler signals, yielding a lowest detectable absorption and optical phase shift of 2.2 x 10(-12) cm(-1) and 4.0 x 10(-12) cm(-1), respectively, both for a 10 s integration time, where the former corresponds to a detection limit of C2H2 of 5 ppt. (C) 2014 Optical Society of America
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| 4. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Use of etalon-immune distances to reduce the influence of background signals in frequency-modulation spectroscopy and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy
- 2014
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 31:12, s. 2938-2945
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Tidskriftsartikel (refereegranskat)abstract
- The detection sensitivity of phase-modulated techniques such as frequency-modulation spectroscopy (FMS) and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is often limited by etalon background signals. It has previously been shown that the impact of etalons can be reduced by the use of etalon-immune distances (EIDs), i.e., by separating the surfaces that give rise to etalons by a distance of q. L-m, where L-m is given by c/2n nu(m), where, in turn, n and nu(m) are the index of refraction between the components that make up the etalon (thus most often that of air) and the modulation frequency, respectively, and where q is an integer (i.e., 1, 2, 3,.) or half-integer (i.e., 1/2, 1, 3/2,.) for the dispersion and absorption modes of detection, respectively. An etalon created by surfaces separated by an EID will evade detection and thereby not contribute to any background signal. The concept of EIDs in FMS and NICE-OHMS is in this work demonstrated, scrutinized, and discussed in some detail. It is shown that the influence of EIDs on the absorption and dispersion modes of detection is significantly different; signals detected at the dispersion phase are considerably less sensitive to deviations from exact EID conditions than those detected at the absorption phase. For example, the FM background signal from an etalon whose length deviates from an EID by 2.5% of L-m (e.g., by 1 cm for an L-m of 40 cm), detected in dispersion, is only 9% of that in absorption. This makes the former mode of detection the preferred one whenever a sturdy immunity against etalons is needed or when optical components with parallel surfaces (e.g., lenses, polarizers, or beam splitters) are used. The impact of the concept of EIDs on NICE-OHMS is demonstrated by the use of Allan-Werle plots.
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| 5. |
- Rutkowski, Lucile, et al.
(författare)
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Experimental 1.5-1.6 μm water line list at 1950 K
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781943580477
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a high-temperature water absorption spectrum measured in a flame using cavity-enhanced frequency comb-based Fourier transform spectroscopy. The retrieved transition intensities and frequencies are assigned using the POKAZATEL line list.
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| 6. |
- Vieira, Francisco Senna, et al.
(författare)
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Robust, Fast and Sensitive Near-Infrared Continuous-Filtering Vernier Spectrometer
- 2020
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Ingår i: 2020 Conference on Lasers and Electro-Optics (CLEO). - : IEEE. - 9781943580767 ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- We present a new robust approach to cavity-enhanced comb spectroscopy based on Vernier filtering, a fixed diffraction grating, custom-made chopper wheel, and a low bandwidth comb-cavity stabilization scheme. We measure a CO2 spectrum with a few GHz resolution and 5 x 10-8 cm-1 sensitivity in 9.4 ms.
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| 7. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
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Broadband molecular detection with cavity-enhanced optical frequency comb spectroscopy
- 2014
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Ingår i: Optical instrumentation for energy and environmental applications, E2 2014. - Washington, D.C. : Optical Society of America (OSA). - 9781557527561
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Konferensbidrag (refereegranskat)abstract
- We demonstrate detection of atmospheric species in air and combustion environment using near-infrared cavity-enhanced optical frequency comb spectroscopy based on an Er:fiber femtosecond laser and a fast-scanning Fourier transform spectrometer.
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| 8. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
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Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared application to trace detection of hydrogen peroxide
- 2013
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer. - 0946-2171 .- 1432-0649. ; 110:2, s. 163-175
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Tidskriftsartikel (refereegranskat)abstract
- 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 3.76 μm 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 5.4×10-9 cm-1 Hz-1/2 with a resolution of 800 MHz is achieved (corresponding to 6.9×10-11 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.
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| 9. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
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Cavity-enhanced optical frequency combs spectroscopy in the near- and mid-infrared
- 2016
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Ingår i: Imaging and applied optics 2016. - : OSA - The Optical Society. - 9781943580156
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Konferensbidrag (refereegranskat)abstract
- We present the recent developments in high-resolution Fourier transform spectroscopy based on optical frequency combs for precision measurements and combustion diagnostics, and the first implementation of continuous-filtering Vernier spectroscopy in the mid-infrared wavelength range for fast multispecies detection.
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| 10. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
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Characterization of fiber-laser-based sub-Doppler NICE-OHMS for quantitative trace gas detection
- 2008
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Ingår i: Optics Express. - 1094-4087. ; 16:19, s. 14689-14702
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Tidskriftsartikel (refereegranskat)abstract
- The potential of fiber-laser-based sub-Doppler noise-immune cavity-enhanced optical heterodyne molecular spectrometry for trace gas detection is scrutinized. The non-linear dependence of the on-resonance sub-Doppler dispersion signal on the intracavity pressure and power is investigated and the optimum conditions with respect to these are determined. The linearity of the signal strength with concentration is demonstrated and the dynamic range of the technique is discussed. Measurements were performed on C2H2 at 1531 nm up to degrees of saturation of 100. The minimum detectable sub-Doppler optical phase shift was 5 x 10-11 cm-1 Hz-1/2, corresponding to a partial pressure of C2H2 of 1 x 10-12 atm for an intracavity pressure of 20 mTorr, and a concentration of 10 ppb at 400 mTorr.
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