Level repulsion of GHz phononic surface waves in quartz substrate with finite-depth holes.
This paper presents numerical and experimental results on the level repulsion of gigahertz surface acoustic waves in an air/ST-cut quartz phononic structure with finite-depth holes. The colorful dispersion with the parameter of the in-plane (sagittal plane) ratio of polarization was adopted to determine the Rayleigh wave bandgap induced by the level repulsion. The results of numerical analyses showed that the frequency and width of the bandgap induced by the level repulsion strongly depend on the geometry of the air holes in the phononic structure. In the experiment, a pair of slanted interdigital transducers with frequency in the gigahertz range was designed and fabricated to generate and receive broadband Rayleigh waves, whereas the reactive ion etching process with electron-beam lithography was used to fabricate submicrometer phononic structures. The measured results of the bandgap induced by the level repulsion agreed favorably with the numerical prediction.
Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan.
Sih-Ling
SL
Yeh
WPI-AIMR, Tohoku University, Sendai 980-0845, Japan.
Yu-Ching
YC
Lin
WPI-AIMR, Tohoku University, Sendai 980-0845, Japan.
Yao-Chuan
YC
Tsai
Department of Mechanical Engineering, Tohoku University, Sendai 980-0845, Japan.
Takahito
T
Ono
Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan. Electronic address: wutt@ntu.edu.tw.
Tsung-Tsong
TT
Wu
Level repulsion; Phononic crystal; Quartz substrate; Surface acoustic wave