Articles | Volume 15, issue 2
https://doi.org/10.5194/jsss-15-141-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/jsss-15-141-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Development and optimization of an OF-CEAS system for stable isotopic ratio analysis of methane (δ13C-CH4) in the mid-infrared
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Ponkanok Nitzsche
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Jens Goldschmidt
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Christian Weber
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Fraunhofer Institute for Physical Measurement Techniques – IPM, Georges-Köhler-Allee 301, 79110 Freiburg, Germany
Leonard Nitzsche
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Katrin Schmitt
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Fraunhofer Institute for Physical Measurement Techniques – IPM, Georges-Köhler-Allee 301, 79110 Freiburg, Germany
Jürgen Wöllenstein
Laboratory for Gas Sensors, Institute for Microsystems Engineering – IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
Fraunhofer Institute for Physical Measurement Techniques – IPM, Georges-Köhler-Allee 301, 79110 Freiburg, Germany
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Sebastian Kindorf, Fabio Gutmann, Christian Weber, Benedikt Bierer, Jürgen Wöllenstein, and Chris Stoeckel
J. Sens. Sens. Syst., 15, 89–97, https://doi.org/10.5194/jsss-15-89-2026, https://doi.org/10.5194/jsss-15-89-2026, 2026
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We present an eight-channel evaluation board for ultrasound sonography and photoacoustic imaging. High frame rates enable averaging, improving signal-to-noise ratio. The board integrates a programmable preamplifier and an analog front-end with 12-bit analog-to-digital conversion, with data transmitted via Ethernet for PC evaluation. Gain distribution and its effect on signal-to-noise ratio in a multichannel photoacoustic receive chain are quantitatively characterized at 540 frames per second.
Simon Gaßner, Simon Essing, David Tumpold, Katrin Schmitt, and Jürgen Wöllenstein
J. Sens. Sens. Syst., 13, 219–226, https://doi.org/10.5194/jsss-13-219-2024, https://doi.org/10.5194/jsss-13-219-2024, 2024
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This article describes a small prototype sensor designed to sense carbon dioxide (CO2) levels for indoor air quality monitoring. The device uses a photoacoustic detector fabricated using a wafer-bonding process. This allows for high-volume production of the sensors. The prototype presented is small in size and can detect CO2 levels as low as 81 ppm with a response time of 53 s. Our results show suitability for application in indoor air quality control systems.
Armin Lambrecht, Carsten Bolwien, Hendrik Fuhr, Gerd Sulz, Annett Isserstedt-Trinke, André Magi, Steffen Biermann, and Jürgen Wöllenstein
J. Sens. Sens. Syst., 12, 123–131, https://doi.org/10.5194/jsss-12-123-2023, https://doi.org/10.5194/jsss-12-123-2023, 2023
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Infrared spectroscopy is great for determining the composition of liquids. Combined with attenuated total reflection (ATR), one can just put the sample on the sensitive surface. We made a compact device with a diamond-coated silicon ATR crystal to protect the surface against aggressive fluids. Silicon crystal, light source and detector are hermetically sealed in a housing. Our tests show that the diamond coating enhanced the sensitivity compared to uncoated ATR elements as predicted by theory.
Max Bergau, Thomas Strahl, Benjamin Scherer, and Jürgen Wöllenstein
J. Sens. Sens. Syst., 12, 61–68, https://doi.org/10.5194/jsss-12-61-2023, https://doi.org/10.5194/jsss-12-61-2023, 2023
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Imaging of greenhouse gases is of great interest due to global warming. A spectroscopic method, using an active illumination of the scene, is presented. It allows for imaging and concentration measurements of much smaller gas plumes and leaks than current state-of-the-art gas cameras (optical gas imaging cameras). A real-time camera is realized and validated using known methane concentrations.
Katrin Schmitt, Mara Sendelbach, Christian Weber, Jürgen Wöllenstein, and Thomas Strahl
J. Sens. Sens. Syst., 12, 37–44, https://doi.org/10.5194/jsss-12-37-2023, https://doi.org/10.5194/jsss-12-37-2023, 2023
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We present a photoacoustic sensor enabling fast, inexpensive, and highly sensitive methane detection in environmental monitoring applications. Six different T-cell designs were both theoretically and experimentally investigated. The aim was to understand the photoacoustic signal generation and resonances in relation to the different cell geometries, and determine the long-term stability and the detection limits for methane. These were below the methane background concentration in air of 1.8 ppm.
Benedikt Bierer, Dario Grgić, Olena Yurchenko, Laura Engel, Hans-Fridtjof Pernau, Martin Jägle, Leonhard Reindl, and Jürgen Wöllenstein
J. Sens. Sens. Syst., 10, 185–191, https://doi.org/10.5194/jsss-10-185-2021, https://doi.org/10.5194/jsss-10-185-2021, 2021
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Detection of flammable gases is necessary to avoid explosive atmospheres. Commercial pellistors require an operation temperature above 450 °C for the detection of methane. We present a novel wireless low-power catalytic gas sensor system based on non-precious metal catalyst for the detection of methane and propane operated at 350 °C. The combination of a MEMS-based sensor with a low-power radio system provides the opportunity to monitor complex infrastructures without using a power grid.
Cited articles
Allan, D. W.: Statistics of atomic frequency standards, Proc. IEEE, 54, 221–230, https://doi.org/10.1109/PROC.1966.4634, 1966.
Amotchkina, T., Trubetskov, M., Hahner, D., and Pervak, V.: Characterization of e-beam evaporated Ge, YbF3, ZnS, and LaF3 thin films for laser-oriented coatings, Appl. Optics, 59, A40–A47, https://doi.org/10.1364/AO.59.000A40, 2020.
Baer, D. S., Paul, J. B., Gupta, M., and O'Keefe, A.: Sensitive absorption measurements in the near-infrared region using off-axis integrated-cavity-output spectroscopy, Appl. Phys. B, 75, 261–265, https://doi.org/10.1007/s00340-002-0971-z, 2002.
Bergamaschi, P., Schupp, M., and Harris, G. W.: High-precision direct measurements of (13)CH(4) (12)CH(4) and (12)CH(3)D (12)CH(4) ratios in atmospheric methane sources by means of a long-path tunable diode laser absorption spectrometer, Appl. Optics, 33, 7704–7716, https://doi.org/10.1364/AO.33.007704, 1994.
Bergin, A. G. V., Hancock, G., Ritchie, G. A. D., and Weidmann, D.: Linear cavity optical-feedback cavity-enhanced absorption spectroscopy with a quantum cascade laser, Opt. Lett., 38, 2475–2477, https://doi.org/10.1364/OL.38.002475, 2013.
Brand, W. A.: High Precision Isotope Ratio Monitoring Techniques in Mass Spectrometry, J. Mass Spectrom., 31, 225–235, https://doi.org/10.1002/(SICI)1096-9888(199603)31:3<225::AID-JMS319>3.0.CO;2-L, 1996.
Crosson, E. R.: A cavity ring-down analyzer for measuring atmospheric levels of methane, carbon dioxide, and water vapor, Appl. Phys. B, 92, 403–408, https://doi.org/10.1007/s00340-008-3135-y, 2008.
Dahnke, H., Kleine, D., Urban, W., Hering, P., and Mürtz, M.: Isotopic ratio measurement of methane in ambient air using mid-infrared cavity leak-out spectroscopy, Appl. Phys. B, 72, 121–125, https://doi.org/10.1007/s003400000509, 2001.
Dunn, P. J. H., Malinovsky, D., Ogrinc, N., Potočnik, D., Flierl, L., Rienitz, O., Paul, D., and Meijer, H. A. J.: Re-determination of R(13C/12C) for Vienna Peedee belemnite (VPDB), Rapid Commun. Mass Sp., 38, e9773, https://doi.org/10.1002/rcm.9773, 2024.
Habig, J. C., Nadolny, J., Meinen, J., Saathoff, H., and Leisner, T.: Optical feedback cavity enhanced absorption spectroscopy: effective adjustment of the feedback-phase, Appl. Phys. B, 106, 491–499, https://doi.org/10.1007/s00340-011-4804-9, 2012.
Helmig, D., Rossabi, S., Hueber, J., Tans, P., Montzka, S. A., Masarie, K., Thoning, K., Plass-Duelmer, C., Claude, A., Carpenter, L. J., Lewis, A. C., Punjabi, S., Reimann, S., Vollmer, M. K., Steinbrecher, R., Hannigan, J. W., Emmons, L. K., Mahieu, E., Franco, B., Smale, D., and Pozzer, A.: Reversal of global atmospheric ethane and propane trends largely due to US oil and natural gas production, Nat. Geosci., 9, 490–495, https://doi.org/10.1038/ngeo2721, 2016.
Kerstel, E., Iannone, R. Q., Chenevier, M., Kassi, S., Jost, H.-J., and Romanini, D.: A water isotope (2H, 17O, and 18O) spectrometer based on optical feedback cavity-enhanced absorption for in situ airborne applications, Appl. Phys. B, 85, 397–406, https://doi.org/10.1007/s00340-006-2356-1, 2006.
Kogelnik, H. and Li, T.: Laser beams and resonators, Appl. Optics, 5, 1550–1567, https://doi.org/10.1364/AO.5.001550, 1966.
Lechevallier, L., Grilli, R., Kerstel, E., Romanini, D., and Chappellaz, J.: Simultaneous detection of C2H6, CH4, and δ13C−CH4 using optical feedback cavity-enhanced absorption spectroscopy in the mid-infrared region: towards application for dissolved gas measurements, Atmos. Meas. Tech., 12, 3101–3109, https://doi.org/10.5194/amt-12-3101-2019, 2019.
Long, D. A., Okumura, M., Miller, C. E., and Hodges, J. T.: Frequency-stabilized cavity ring-down spectroscopy measurements of carbon dioxide isotopic ratios, Appl. Phys. B, 105, 471–477, https://doi.org/10.1007/s00340-011-4518-z, 2011.
Manfred, K. M., Ciaffoni, L., and Ritchie, G. A. D.: Optical-feedback cavity-enhanced absorption spectroscopy in a linear cavity: model and experiments, Appl. Phys. B, 120, 329–339, https://doi.org/10.1007/s00340-015-6140-y, 2015.
Masson-Delmotte, V. P., Zhai, A., Pirani, S. L., Connors, C., Péan, S., Berger, N., Caud, Y., Chen, L., Goldfarb, M. I., Gomis, M., Huang, K., Leitzell, E., and Lonnoy, J.: IPCC, 2021: Climate Change 2021: The Physical Science Basis, Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, https://doi.org/10.1017/9781009157896, 2023.
McManus, J. B., Kebabian, P. L., and Zahniser, M. S.: Astigmatic mirror multipass absorption cells for long-path-length spectroscopy, Appl. Optics, 34, 3336–3348, https://doi.org/10.1364/AO.34.003336, 1995.
McManus, J. B.: Application of quantum cascade lasers to high-precision atmospheric trace gas measurements, Opt. Eng., 49, 111124, https://doi.org/10.1117/1.3498782, 2010.
Morville, J., Kassi, S., Chenevier, M., and Romanini, D.: Fast, low-noise, mode-by-mode, cavity-enhanced absorption spectroscopy by diode-laser self-locking, Appl. Phys. B, 80, 1027–1038, https://doi.org/10.1007/s00340-005-1828-z, 2005.
Morville, J., Romanini, D., Chenevier, M., and Kachanov, A.: Effects of laser phase noise on the injection of a high-finesse cavity, Appl. Optics, 41, 6980–6990, https://doi.org/10.1364/AO.41.006980, 2002.
Myhre, G. D., Shindell, F.-M., Bréon, W., Collins, J., Fuglestvedt, J., Huang, D., Koch, J.-F., Lamarque, D., Lee, B., Mendoza, T., Nakajima, A., Robock, G., Stephens, T., Takemura, T. and Zhang, H.: An thropogenic and Natural Radiative Forcing, in: Climate Change 2013: The Physical Science Basis, Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, 659–740, https://doi.org/10.1017/CBO9781107415324.018, 2014.
Nyquist, H.: Certain Topics in Telegraph Transmission Theory, Trans. Am. Inst. Electr. Eng., 47, 617–644, https://doi.org/10.1109/T-AIEE.1928.5055024, 1928.
Ohshima, S. and Schnatz, H.: Optimization of injection current and feedback phase of an optically self-locked laser diode, J. Appl. Phys., 71, 3114–3117, https://doi.org/10.1063/1.351006, 1992.
O'Keefe, A.: Integrated cavity output analysis of ultra-weak absorption, Chem. Phys. Lett., 293, 331–336, https://doi.org/10.1016/S0009-2614(98)00785-4, 1998.
Patimisco, P., Scamarcio, G., Tittel, F. K., and Spagnolo, V.: Quartz-enhanced photoacoustic spectroscopy: a review, Sensors (Basel, Switzerland), 14, 6165–6206, https://doi.org/10.3390/s140406165, 2014.
Quay, P., Stutsman, J., Wilbur, D., Snover, A., Dlugokencky, E., and Brown, T.: The isotopic composition of atmospheric methane, Global Biogeochem. Cy., 13, 445–461, https://doi.org/10.1029/1998GB900006, 1999.
Schaefer, H., Mikaloff Fletcher, S. E., Veidt, C., Lassey, K. R., Brailsford, G. W., Bromley, T. M., Dlugokencky, E. J., Michel, S. E., Miller, J. B., Levin, I., Lowe, D. C., Martin, R. J., Vaughn, B. H., and White, J. W. C.: A 21st-century shift from fossil-fuel to biogenic methane emissions indicated by 13CH4, Science (New York, NY), 352, 80–84, https://doi.org/10.1126/science.aad2705, 2016.
Shannon, C. E.: Communication in the Presence of Noise, P. IRE, 37, 10–21, https://doi.org/10.1109/JRPROC.1949.232969, 1949.
Tuzson, B., Mohn, J., Zeeman, M. J., Werner, R. A., Eugster, W., Zahniser, M. S., Nelson, D. D., McManus, J. B., and Emmenegger, L.: High precision and continuous field measurements of δ13C and δ18O in carbon dioxide with a cryogen-free QCLAS, Appl. Phys. B, 92, https://doi.org/10.1007/s00340-008-3085-4, 2008.
Werle, P., Mcke, R., and Slemr, F.: The limits of signal averaging in atmospheric trace-gas monitoring by tunable diode-laser absorption spectroscopy (TDLAS), Appl. Phys. B, 57, 131–139, https://doi.org/10.1007/BF00425997, 1993.
Werle, P.: A review of recent advances in semiconductor laser based gas monitors, Spectrochim. Acta A, 54, 197–236, https://doi.org/10.1016/S1386-1425(97)00227-8, 1998.
Zellweger, C., Emmenegger, L., Firdaus, M., Hatakka, J., Heimann, M., Kozlova, E., Spain, T. G., Steinbacher, M., van der Schoot, M. V., and Buchmann, B.: Assessment of recent advances in measurement techniques for atmospheric carbon dioxide and methane observations, Atmos. Meas. Tech., 9, 4737–4757, https://doi.org/10.5194/amt-9-4737-2016, 2016.
Short summary
Methane plays an important role in global warming, and tracing its sources requires precise analysis of its isotopic fingerprint. In this study, we demonstrate the foundation of a system based on optical feedback cavity-enhanced absorption spectroscopy that achieves the stability needed for accurate isotope measurements. This work shows the potential of the method for future climate studies and environmental monitoring.
Methane plays an important role in global warming, and tracing its sources requires precise...