Technological projects portfolio


Photoacoustic gas analyzer with real-time trace detection

Investment: €477k

Scope: Agriculture and Environment

Scientific field(s): Physics–Chemistry and Optics

Institution(s): ONERA

Development: Technology to be marketed

#GasDetection #Photoacoustic


With the increase in the number of applications requiring gas detection (safety, industry, health, environment) there is an increased need for versatile, compact and sensitive sensors.

The most common solutions for making these measurements are based on electrochemical technologies, flame ionisation, chemiluminescence, mass spectroscopy, and various optical methods including photo-acoustics. Photo-acoustics involves detecting pressure waves generated by the “absorption/relaxation” process that takes place in gas molecules, by the modulation frequency of the excitation laser.


In general, optical technologies offer an optimal compromise between sensitivity, selectivity, portability and cost. Unlike other optical sensing technologies, photo-acoustics enables multi-gas detection at a reduced cost. To detect different gases, it is only necessary to change the wavelength of the laser emission, whereas for other optical technologies it is also necessary to adapt the sensor array and the optical elements. Photo-acoustics makes it possible to retain a very good limit of detection, while increasing compactness and reducing costs. The linearity of the response with the concentration of gas should also be noted, as well as the very high dynamic measurement range.

This technique nevertheless has a major defect, which is its sensitivity to surrounding background noise and vibrations, which can be reduced by using high quality factor resonators. However, this type of resonator causes inevitable frequency drifts (due to heat, change in the measurement environment etc.) requiring continuous calibration of the sensor. This sensitivity represents a major brake on the deployment of this method in industry.

In response, the GASPARD Project proposes a significant development in the technology based on the use of an optimised resonator and innovative detection electronics. This sensor array should make it possible to significantly improve stability and greatly reduce sensitivity to background noise, while increasing the bandwidth and the measurement resolution.


Once these developments have been made and validated, the target market is that of medium and high-performance gas analysis apparatus.

The intended applications are detection of gas emissions in industrial systems, control of chemical processes, and monitoring of air quality.