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B. Lendl:
"Potential of quantum cascade laser spectroscopy for the analysis of liquids - commercial realization and new developments";
Vortrag: Seminar an der Universität Bari, Bari (eingeladen); 27.04.2012.

The continued development of mid-IR quantum cascade lasers (QCL) is of considerable interest for the development of portable sensor systems designed for the quantitative and qualitative analysis of gases and liquids. Recent developments include commercially available broadly tuneable external cavity (EC) QCLs with steadily increasing spectral tuning range and spectral power densities, as well as research type ring QCLs, which allow the realization of several discrete wavelengths out of one gain medium, and integration of these in one device.
This presentation will introduce these two types of multi-wavelength QCL light sources by reporting on results from characterizing their respective emission characteristics using time resolved step-scan FTIR spectroscopy. Furthermore, application in the field of liquid and gas phase measurements will be shown. For measurement of liquids, two options of a sample / QCL interface will be introduced. On the one hand, transmission measurements will be shown using the example of the determination of the oil content in the process water of the petrochemical industry, as well as on the quantitative determination of glucose, lactate and other blood parameters from human serum. In addition, results on the use of planar waveguides, made out of MgF2 and SiN, will be shown as well. The latter sampling interface improves on the conventional attenuated total reflection (ATR) technique as a more efficient interaction between the QCL light and the liquid sample can be achieved. Furthermore, it is planned to report briefly on recent QCL based gas measurements employing quartz enhanced photoacoustic detection for the quantification of SO2 in the ppbv concentration range.