Laboratory Integration and Testing #2 and #11 (LIT#2 and LIT#11) have been conducted remotely in November 2020 and May 2021, respectively, at Alpes Lasers (Switzerland) and Technische Universität Wien, TUW (Austria) premises with the purpose to show the progress made regarding the development of a fully fiber coupled gas sensor based on the concept of interferometric cavity-assisted photothermal spectroscopy (ICAPS). The mid-IR quantum cascade laser (QCL) developed by Alpes Lasers is an important component of the gas sensor to be developed by TUW.

LIT#2 was the opportunity to present the technologies from Alpes Lasers and TUW to the first responders. In particular, Alpes Lasers presented the concept of quantum cascade lasers and its role in a gas sensor, laser packaging into a high-heat load housing and fibre coupling. Concerning TUW, it was the opportunity to describe the ICAPS sensor scheme, present the first result on CO detection with a Xarion microphone and make a laboratory demonstration.

2nd round of LITs


At the time of LIT#11, one laser for CO has been provided by Alpes Lasers in a commercial HHL packaging and the wavelength requirement for NH3 sensing has been collected by Alpes Lasers from TUW. Alpes Lasers reported a 50% coupling efficiency using commercial fiber couplers from Thorlabs. Due to not satisfactory performance when tuning the laser wavelength a dedicated development is now planned. Simulations on the envisioned version of a “pigtailed” fiber coupling were presented. Also plans were shown indicating that two separate fibers are planned for delivering the two different wavelengths as required for CO and NH3, respectively. A sketch was shown that a single lens would be used to focus the output of both fibers, with the nature of the fibers still to be defined.

TUW presented the experimentally realized fiber coupled readout system for the ICAPS gas sensor using a telecom laser including successful realization of two locking schemes, one based on wavelength modulation and the other on a constant height mode. Furthermore, a working software lock-in amplifier programmed in LabView to replace the bulky bench-top lock-in amplifier from Stanford Research Systems was shown as well. Experimental results on CO detection reaching a limit of detection in the low ppb concentration range were reported, too. For these experiments, the QCL provided by Alpes Laser could be used only after removal of the provided fiber coupling due to significant feedback, detected by TUW, which impaired successful measurements.

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