A group at the TU Wien and Friedrich-Alexander University, who are partners with Alpes Lasers through the Hydroptics and WaterSpy project, have recently published a paper titled “Polarimetric Balanced Detection: Background-Free Mid-IR Evanescent Field Laser Spectroscopy for Low-Noise, Long-term Stable Chemical Sensing” which uses a QC-XT laser from Alpes Lasers to measure water quality in situ at the Prato water treatment plant in Genova, Italy.

By using different mirror configurations, the QC-XT laser can be rapidly switched between different configurations, allowing rapid multi-point sampling and/or scanning. 

In this study, the QC-XT proved to be superior to classic DFB-QCLs due to the broad tuning capabilities of this novel laser type. In addition, unused spectral information for data interpretation was used as an inherent stability control of the system.