Optical observation technique for SH‐type surface acoustic wave

Abstract

AbstractA new technology has been developed for optically visualizing the intensity distribution of the acoustic wave within a surface acoustic wave (SAW) device. In this technique, the strain generated by the SH (Shear Horizontal) wave in a LiTaO3 crystal is detected via the photoelastic effect as a change of polarization state of the light passing through the device. By detecting the SH component, which is the main component of the SAW on a 42°YX LiTaO3, the method provides for more direct observation of the behavior of the acoustic wave in a device than in the conventional technique that detects the SV (Shear Vertical) component, a secondary component. Based on the present technique, an acoustic wave observation setup is developed and a simple resonator is evaluated. It is found that the acoustic‐wave distributions within an IDT depend on the driving frequencies and that acoustic wave energy is leaked outside the resonator at specific frequencies. Further, a more accurate visualization of the acoustic wave component is made possible by correcting for the influence of the electro‐optical effect on the observation results. Another setup has been developed in which a probe light beam is incident from the back side of the substrate and the light reflected from the device surface is used in order to determine the distribution under an electrode. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(6): 10–17, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20066