Study of Layered-Structure Phononic Crystals for Surface Acoustic Waves

Phononic crystal (PC) is a new acoustic metamaterial composed of periodic media or periodic geometric structures. Its important properties include anisotropic propagation and acoustic band gaps. Various PC structures were observed for bulk acoustic wave, surface acoustic wave (SAW), and Lamb waves respectively. Then many PC applications which are potential to be used as acoustic-electronic components were designed accordingly, such as filters, reflective gratings, waveguides, and resonant cavities. Among the commercial acoustic-electronic components, SAW devices are widely used and suitable to combine with PCs. Currently, to make the fabrication feasible, the PCs used in SAW devices usually consist of cylindrical air holes with high aspect ratio in the matrix and no additional materials were inserted in the holes. However, there are still many limitations to make PC for SAWby etching deep holes on substrates. In this project, the potential layered-stricture PCs for SAW will be investigated to make the fabrication and the possible applications more feasible. Firstly, finite element (FE) method will be adopted and modified to analyze SAWs in layered-structure PC structures. Band gaps and anisotropic property of SAWs in the PC can be analyzed accordingly. The geometric designs and the materials in the layered-structure PCs will be varied to investigate the better design for control the SAW propagation. In the experimental side, millimeter-scale layered-structure PCs will be designed and fabricated on a metal substrate. Ultrasonic transducers will be used to measure SAWs signal. The experimental results will be compared with the numerical analyses. The study is expected to be valuable for the realization of applying PCs in SAWdevices operating in high frequency range.

Project ID:PB10107-1732
External Project ID:NSC101-2221-E182-026