[Zurück]

B. Lendl, J. Hayden, S. Lindner, A. Schwaighofer, M. Montemurro, Paul Waclawk, A. Genner, H. Moser:
"Recent Advances in QCL Based Sensing of Gases and Liquids";
Vortrag: 14th International Conference on Mid-IR Optoelectronics: Materials and Devices MIOMD, Flagstaff, Arizona (eingeladen); 07.10.2018 - 10.10.2018.

Advances in Analytical Chemistry are often linked to technological developments in
neighboring disciplines. This also concerns the recent development of quantum cascade
lasers, which allows realization of sensing approaches in the mid-IR range that are different
and potentially more powerful compared to classical absorption measurements based on
Lambert-Beer law. In this presentation, new approaches for gas and liquid sensing as well as
different applications using quantum cascade lasers will be discussed.
In the field of trace gas sensing indirect methods such as photothermal and photoacoustic
techniques are very promising as their analytical signal is directly proportional to the analyte
concentration and the employed laser power. This presentation will focus on recent advances
in Photothermal Interferometry (PTI) employing distributed feedback Quantum Cascade
Lasers. LODs in the single digit ppb range for SO2 have been recently achieved when
working in a balanced detection mode.
For liquid sensing external cavity Quantum Cascade Lasers are used. The latest generation
of these lasers finally allows to outperform state-of-the-art FTIR spectrometers in terms of
signal to noise in the recorded absorbance spectra. In this presentation special focus will be
given to the qualitative and quantitative analysis of proteins in aqueous media in the spectral
region from 1530-1700 cm-1. On the example of milk analysis it will be shown how different
milk proteins (casein, β-lactoglobulin,..) can be distinguished and simultaneously quantified.
Finally, a Mach Zehnder interferometer for performing dispersion and absorption
spectroscopy of liquid samples will be introduced. The operation principle will be outlined
and examples for sugar analysis in aqueous solution presented. Using refractive index spectra
in the spectral range from 1000-1200 cm-1 quantitative analysis of ternary sugar samples will
be shown.