QCL-IR Dispersion Spectroscopy

Acquisition of classical absorption spectra of liquids in the mid-IR range with QCLs is often limited in sensitivity by noise from the laser source. Alternatively, measurement of molecular dispersion (i.e., refractive index) spectra poses an experimental approach that is immune to intensity fluctuations and further offers a direct relationship between the recorded signal and the sample concentration.

In dispersion spectroscopy, the phase shift of the radiation due to passing through a sample is measured. Dispersion and absorption are caused by the same process, thus the same spectral information about the sample can be retrieved by determining either of the two properties.

Very recently, we introduced a Mach-Zehnder interferometer setup to measure the absorption and dispersion spectra of liquid samples.

Key Publications:

The next generation of mid-IR laser-based refractive index (dispersion) spectroscopy of liquid-phase analytes, SPIE Proceedings, 2022., opens an external URL in a new window

Mid-IR refractive index sensor for detecting proteins employing an external cavity quantum cascade laser-based Mach-Zehnder interferometer, Optics Express, 2020., opens an external URL in a new window 

Beyond Beer’s law – why the index of refraction depends (almost) linearly on concentration, ChemPhysChem, 2020., opens an external URL in a new window

External Cavity Quantum Cascade Laser-Based Mid-Infrared Dispersion Spectroscopy for Qualitative and Quantitative Analysis of Liquid-Phase Samples, Applied Spectroscopy, 2019., opens an external URL in a new window



Andreas Schwaighofer

Alicja Dabrowska