Excitation and detection of evanescent acoustic waves in piezoelectric plates: Theoretical and 2D FEM modeling

•Detection of evanescent waves is possible when real part of their velocity is more than imaginary one.•Detection of evanescent waves is possible by using set of IDT with various spatial periods.•The frequency range of detectable evanescent waves is more for stronger piezoelectric materials.•Evanesc...

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Bibliographic Details
Published in:Ultrasonics 2019-11, Vol.99, p.105961-105961, Article 105961
Main Authors: Kuznetsova, Iren, Nedospasov, Ilya, Smirnov, Andrey, Qian, Zheng-hua, Wang, Bin, Dai, Xiao-yun
Format: Article
Language:English
Subjects:
Backward waves
Evanescent waves
Interdigital transducers
Piezoelectric plates
ZGV point
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Summary:•Detection of evanescent waves is possible when real part of their velocity is more than imaginary one.•Detection of evanescent waves is possible by using set of IDT with various spatial periods.•The frequency range of detectable evanescent waves is more for stronger piezoelectric materials.•Evanescent waves could be used for high sensitive sensors. This paper presents the results of the theoretical and 2D FEM modeling excitation and detection of evanescent acoustic waves in piezoelectric plates. By application of 2D ordinary differential equations derived by Auld, we obtained the dispersion curves of A1 and SH1 waves in YX LiNbO3 and YX KNbO3 plates in proximity to a zero group velocity point. The branches corresponding to evanescent acoustic waves are distinguished. A frequency range where real part of evanescent wave velocity is more than imaginary one was found. In this region evanescent mode is characterized by opposite directions of the phase and group velocities, i.e. this is backward wave. The theoretical analysis was verified in commercial 2D FEM software COMSOL 5.3. By modeling a set of interdigital transducers placed on the surface of Y-cut LiNbO3 wafer with various values of the spatial period we found the resonant frequencies corresponding to evanescent A1 mode. Due to proximity of this wave to a zero group velocity point its properties should be extremely sensitive to change of waveguide quality and ambient air. This is open the possibility to use these waves for development of high sensitive sensors and for nondestructive waveguide analysis.
ISSN:0041-624X
1874-9968
DOI:10.1016/j.ultras.2019.105961