Skewed waves for anisotropic material characterization

Abstract: Guided elastic waves emerge in thin or slender structures. They are important for many applications, including complex material evaluation, sensing and telecommunication electronics. My presentation focuses on the physical peculiarities of guided waves in anisotropic layered media and how this can be exploited in the context of material characterization. We will first address so-called zero-group-velocity (ZGV) resonances, which are guided waves with vanishing power flux. They explain the beautiful beating resonance pattern that emerges naturally at the surface of a wafer after a short point-source excitation. Furthermore, we find waves propagating with transverse-group velocity (TGV) that are radiated along a line source instead of away from the source as would be conventionally the case.

I will sketch the theory and present original measurements of these two effects. They are both a consequence of the skew angle between the wave's power flux and its wave vector. We will end with a comprehensive understanding of the general power flux skewing phenomenon and its great potential for effective in situ material evaluation of modern microelectronic devices. 

Le mardi 18 novembre 2025 à 11h00 / Amphithéâtre François Canac, LMA

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