Kotel'nikov Institute of Radio Engineering and Electronics of RAS, Moscow 125009, Russia.
Kotel'nikov Institute of Radio Engineering and Electronics of RAS, Moscow 125009, Russia.
Ultrasonics. 2019 Nov;99:105961. doi: 10.1016/j.ultras.2019.105961. Epub 2019 Jul 10.
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 A and SH waves in YX LiNbO and YX KNbO 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 LiNbO wafer with various values of the spatial period we found the resonant frequencies corresponding to evanescent A 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.
本文介绍了在压电板中激发和检测消逝波的理论和 2D 有限元建模的结果。通过应用 Auld 推导出的 2D 常微分方程，我们得到了接近零群速度点的 YX LiNbO 和 YX KNbO 板中 A 波和 SH 波的频散曲线。区分了对应于消逝声波的分支。发现了消逝波速度的实部大于虚部的频率范围。在这个区域，消逝模的相位和群速度方向相反，即这是反向波。理论分析在商业 2D 有限元软件 COMSOL 5.3 中得到了验证。通过对具有不同空间周期的 Y 切 LiNbO 晶片表面的一组叉指换能器进行建模，我们找到了对应于消逝 A 模的谐振频率。由于该波接近零群速度点，其性质应该对波导质量和环境空气的变化极其敏感。这为开发高灵敏度传感器和非破坏性波导分析开辟了可能性。
