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A quantum cascade laser-based Mach-Zehnder interferometer for chemical sensing employing molecular absorption and dispersion

: Hayden, Jakob; Hugger, Stefan; Fuchs, Frank; Lendl, Bernhard

Volltext urn:nbn:de:0011-n-5067468 (1.0 MByte PDF)
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Erstellt am: 24.8.2018

Applied Physics. B 124 (2018), Art. 29, 9 S.
ISSN: 0340-3793
ISSN: 0721-7269
ISSN: 0946-2171
ISSN: 1432-0649
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IAF ()

We employ a novel spectroscopic setup based on an external cavity quantum cascade laser and a Mach–Zehnder interferometer to simultaneously record spectra of absorption and dispersion of liquid samples in the mid-infrared. We describe the theory underlying the interferometric measurement and discuss its implications for the experiment. The capability of simultaneously recording a refractive index and absorption spectrum is demonstrated for a sample of acetone in cyclohexane. The recording of absorption spectra is experimentally investigated in more detail to illustrate the method’s capabilities as compared to direct absorption spectroscopy. We find that absorption signals are recorded with strongly suppressed background, but with smaller absolute sensitivity. A possibility of optimizing the setup’s performance by unbalancing the interferometer is presented.