Abstract
We developed a new technique for the detection of shear horizontal surface acoustic waves (SH-SAW) using a one-dimensional laser-based Doppler vibrometer. It measures the out-of-plane surface deformation at the fingertip of an interdigitated transducer (the boundary of the wave aperture) and uses it to estimate the instantaneous in-plane displacement field given the substrate Poisson ratio. It can also estimate the degree of surface confinement (wave decay rate). The proposed approach was first verified using finite element analysis (FEA) and demonstrated experimentally using a Bleustein–Gulyaev resonator.
Highlights
Assuming that the vibrometer-measured displacement represents the average surface deformation within the field illuminated by the spot, Figure 5 can be used to estimate the decay rate r given the spot size
This is reasonable considering that the metallization of the interdigitated electrodes (IDTs) enhances the confinement of the wave to the substrate surface [40]
We developed a novel technique that uses a 1D Laser Doppler Vibrometer to detect and characterize shear horizontal surface acoustic waves (SH-SAWs)
Summary
For SAW devices based on semi-transparent substrates, such as lithium tantalate, one approach involves passing a laser beam through the material and observing polarization changes due to shear strain [24] This method does not apply to opaque substrates or those covered with opaque films. The tilt angle creates challenges that increase the complexity of the experimental setup It is not applicable for SAWs that have few or no erect structures on the substrate surface, except for the IDT.
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