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.