Accuracy of the determination of propagation velocities of phononic waves in the material

We propose to estimate the error on the frequencies obtained when using the method of Brillouin Light Scattering (BLS). This method of characterization makes it possible to determine a frequency shift in the microwave domain. This shift corresponds to the speed of propagation of the phononic waves inside or on the surface of the material that one wants to characterize. The question arises as to how precisely the microwave frequency will be given. We feel that this will depend on several factors such as the direction and dispersion of the laser signal, but also the characteristics of the instruments used. We therefore refer to the Guide of Uncertainties Measurements (GUM). This guide edited by the 'Bureau International de Poids et Mesures' (BIPM) makes it possible to have a tool in the estimate of the error that one seeks to determine. In this poster, it is shown that the accuracy of the determination of the propagation speed can be of a few percent.