Dispersion and Polarization of Surface Waves Trapped in High Aspect Ratio Electrode Arrays

Vincent Laude, Maria Bayard Dühring, Hanane Moubchir, Naima Khelfaoui, Abdelkrim Khelif

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearch


    Interdigital transducers (IDT) is a classical technique for surface acoustic wave transduction. Usual IDT's make use of electrodes with limited heights, so that surface mode properties do not differ significantly from those of a free or a fully metalized surface. We have proposed previously (J Appl.Phys., 90(5):2492, 2001; Appl. Phys. Lett., 89:083515, 2006.) an experimental and theoretical analysis of the transduction of SAW under a metallic array of electrodes with a large aspect ratio on a piezoelectric substrate, whereby allowing the electrode height to become larger than one wavelength. The multimode character of SAW propagation was observed and the explicit dependence of the SAW velocities as a function of the electrode height was obtained experimentally. Up to a 10-fold slowing of surface waves was observed, with the phase velocity dropping from 4000 m/s down to 450 m/s. We present additional results on the polarization and the dispersion of the surface waves trapped by high aspect ratio electrode arrays. A finite element model, including periodic boundary conditions along the propagation direction and a perfectly matched layer (PML) to absorb waves away from the surface, was implemented. The modal shapes of all resonances can thus be identified precisely, giving access to the polarization of the surface waves. In addition, the vertical vibrations of the IDT surface were monitored using a heterodyne optical probe and confirm computations. The dispersion of the surface modes was further characterized by computing maps of the harmonic admittance and polarization as a function of frequency and wave vector. From these maps, band diagrams are obtained and complete the picture of the dispersion of the trapped surface modes. In particular, the group velocity can be obtained for all wave vector values.
    Original languageEnglish
    Title of host publicationIEEE Ultrasonics Symposium Proceedings
    Publication date2007
    ISBN (Print)978-1-4244-1384-3
    Publication statusPublished - 2007
    Event2007 IEEE Ultrasonics Symposium - New York, United States
    Duration: 28 Oct 200731 Oct 2007


    Conference2007 IEEE Ultrasonics Symposium
    Country/TerritoryUnited States
    CityNew York
    Internet address


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