A layered SAW device using phononic-crystal reflective gratings

In this paper, a design which combines two-port surface acoustic wave (SAW) devices and phononic crystals acting as reflected gratings is demonstrated for the first time. Finite-difference time-domain method is used to analyze the phenomena of surface acoustic waves encountering the phononic crystal grating. The simulation shows that reflected surface acoustic waves result in resonant waves, and this helps to optimize the frequency response of the two-port SAW device. A layered ZnO/Si SAW device and a square lattice phononic crystal composed of cylindrical holes on the silicon half space were fabricated. The phononic crystal has a band gap of 194-223 MHz for surface acoustic waves along the GammaX direction. With the phononic crystal of fifteen-layer cylinders, experimental insertion loss shows a 7-dB improvement at the 212 MHz central frequency than the case without gratings. This newly proposed structure may provide a new idea for designs of resonators, filters, or other possible applications.