Project »ISLAS«

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

Detecting trace gases sensitively in real time, with a compact and easy-to-operate device - this is the aim of the ISLAS project.

In this project funded by the Fraunhofer-Gesellschaft, Fraunhofer IPM and Fraunhofer IAF are working together to develop 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 are developed at Fraunhofer IPM; Fraunhofer IAF develops the light sources and optical resonators.

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 is being 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

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 sensitively.