Polarimetric balanced detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing

Freitag S, Bär M, Buntzoll L, Ramer G, Schwaighofer A, Schmauß B, Lendl B (2021)

Publication Type: Journal article

Publication year: 2021

Journal

ACS Sensors American Chemical Society (ACS)

Abstract

In this work, we introduce polarimetric balanced detection as a new attenuated total reflection (ATR) infrared (IR) sensing scheme, leveraging unequal effective thicknesses achieved with laser light of different polarizations. We combined a monolithic widely tunable Vernier quantum cascade laser (QCL-XT) and a multibounce ATR IR spectroscopy setup for analysis of liquids in a process analytical setting. Polarimetric balanced detection enables simultaneous recording of background and sample spectra, significantly reducing long-term drifts. The root-mean-square noise could be improved by a factor of 10 in a long-term experiment, compared to conventional absorbance measurements obtained via the single-ended optical channel. The sensing performance of the device was further evaluated by on-site measurements of ethanol in water, leading to an improved limit of detection (LOD) achieved with polarimetric balanced detection. Sequential injection analysis was employed for automated injection of samples into a custom-built ATR flow cell mounted above a zinc sulfide multibounce ATR element. The QCL-XT posed to be suitable for mid-IR-based sensing in liquids due to its wide tunability. Polarimetric balanced detection proved to enhance the robustness and long-term stability of the sensing device, along with improving the LOD by a factor of 5. This demonstrates the potential for new polarimetric QCL-based ATR mid-IR sensing schemes for in-field measurements or process monitoring usually prone to a multitude of interferences.

Authors with CRIS profile

Matthias Bär Professur für Hochfrequenztechnik mit dem Schwerpunkt Optische Hochfrequenztechnik und Photonik Laura Buntzoll Lehrstuhl für Hochfrequenztechnik (LHFT) Bernhard Schmauß Professur für Hochfrequenztechnik mit dem Schwerpunkt Optische Hochfrequenztechnik und Photonik

Involved external institutions

Technische Universität Wien / Vienna University of Technology

Austria (AT)

How to cite

APA:

Freitag, S., Bär, M., Buntzoll, L., Ramer, G., Schwaighofer, A., Schmauß, B., & Lendl, B. (2021). Polarimetric balanced detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing. ACS Sensors. https://doi.org/10.1021/acssensors.0c01342

MLA:

Freitag, Stephan, et al. "Polarimetric balanced detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing." ACS Sensors (2021).

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