Influence of layer thickness on time domain Brillouin scattering oscillation amplitude in multilayer films

This paper investigates the impact of a sample structure on the amplitude of time-domain Brillouin scattering (TDBS) oscillations using silicon wafers with different oxide layer thicknesses as an example. According to the calculation results based on transfer matrix theory and Green’s function, along with experimental results, we discovered that the amplitude of TDBS exhibits dual peaks corresponding to the thickness of the silicon dioxide layer, highlighting the TDBS’s acute sensitivity to an internal sample structure. Furthermore, our computational results indicate that both the roughness of the sample and the non-monochromatic nature of the probe light affect the time-domain Brillouin scattering signal, underscoring the significant role of interference effects in TDBS detection. The outcomes of this study suggest that by precisely designing the thickness of the transducer layer, the time-domain Brillouin scattering signal can be enhanced, and it may be possible to determine the roughness of the sample using the amplitude of the time-domain Brillouin oscillation. This is beneficial for improving the detection accuracy of time-domain Brillouin scattering and for extracting a broader range of physical information from TDBS oscillations.