Conference paper
Dispersion and Polarization of Surface Waves Trapped in High Aspect Ratio Electrode Arrays
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.
Language: | English |
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Publisher: | IEEE |
Year: | 2007 |
Pages: | 175-178 |
Proceedings: | 2007 IEEE Ultrasonics Symposium |
ISBN: | 1424413834 , 1424413842 , 150908214X , 150908214x , 9781424413836 , 9781424413843 and 9781509082148 |
ISSN: | 15513025 and 10510117 |
Types: | Conference paper |
DOI: | 10.1109/ULTSYM.2007.55 |
Acoustic transducers Acoustic waves Boundary conditions Electrodes Finite element methods Optical polarization Optical surface waves Perfectly matched layers SAW propagation Surface acoustic waves Surface waves aspect ratio electrode arrays finite element analysis finite element model interdigital transducers perfectly matched layer piezoelectric substrate surface acoustic wave transducers surface acoustic wave transduction surface acoustic waves surface wave dispersion surface wave polarization ultrasonic transducers velocity 4000 m/s velocity 450 m/s