Fraunhofer Institute for Physical Measurement Techniques IPM
Fraunhofer Institute for Physical Measurement Techniques IPM

»ISLAS« project (completed)

Intra-cavity laser spectroscopy for the highly sensitive determination of trace gases

In this project funded by the Fraunhofer-Gesellschaft, Fraunhofer IPM and Fraunhofer IAF have jointly developed a measuring method for the analysis of gas samples. The method is based on a patented approach using the principle of photothermal spectroscopy. Through the combination of three technical tricks, the developed measuring systems become compact and sensitive at the same time:

  • The use of mid-infrared laser radiation from quantum cascade lasers allows us to examine the strongest characteristic absorptions of the target substances.
  • The incorporation of the spectroscopic sensor into a laser resonator ensures a strongly increased interaction of the investigated gas with the excitation laser radiation.
  • The photothermal sensor does not measure miniscule attenuations of the excitation radiation, but instead the local heating of the gas caused by the laser radiation. A measurement signal appears only in the presence of an absorbing substance.

The local heating is measured in an interferometric procedure, the so-called »Photothermal Common-Path Interferometry« (PCI). PCI allows for high sensitivity combined with a compact design of the sensor.

The measuring method and process were developed at Fraunhofer IPM; Fraunhofer IAF developed the light sources and optical resonators. With the »MicroVolume Photothermal Gas Analyzer« (MVP), the project has resulted in a technology demonstration system in the form of a stand-alone tabletop device. The primary goal is to measure trace gases in the human breath. The so-called »biomarkers« detectable in the breath are indicators for monitoring metabolic processes or for patient-oriented, non-invasive medical diagnostics. Besides, there are many other applications for the sensitive detection of trace gases, for example in workplace monitoring, search for hazardous substances, as well as in environmental and process control.

Project finance

The project ISLAS was funded by the internal MAVO program of the Fraunhofer-Gesellschaft.

Project partners

Fraunhofer IPM, Fraunhofer IAF

Project duration

1.3.2019 until 28.2.2022

Further information

© Fraunhofer IPM

Measuring principle

Trace gases are detected by means of their heating in the strong light field of a laser resonator. The heating is read out by a second laser interferometrically and thus highly sensitiv

Demonstrator system

 

In the »ISLAS« project, together with Fraunhofer IAF we have developed a technology demonstrator system – the »MicroVolume Photothermal Gas Analyzer« (MVP). The analyzer – a standalone tabletop sytem – is configured for sensing of ammonia (NH3 ), sampled e.g. from human breath. Target species can be selected by swap of the excitation laser.

Publication

The project results were presented in 2023 at the CLEO/Europe-EQEC conference in Munich.

Detecting breath gas in real-time