Complete bandgap SAW phononic resonant topologies

Resonant surface acoustic wave (SAW) structures employing 2D phononic gratings with hexagonal symmetry are micro-fabricated and tested in a proof of principle study. The proposed structures have the advantage of being compatible with the planar SAW technology, while ensuring operation within the complete frequency bandgap of the phononic grating. More specifically, 2D phononic gratings exhibiting a complete frequency bandgap are employed in the design of three distinct types of resonant test structures. The proposed test structures are fabricated on to a 128° YX LiNbO₃ substrate by means of low resolution photolithography. Frequency response measurements of the SAW phononic resonators confirmed operation within the complete frequency bandgap of each grating structure. The experimental results obtained demonstrate that surface phononic gratings can be successfully used in the design of SAW resonators. The proposed research paves the way for subsequent implementation of the phononic bandgap technology in high performance micro-acoustic RF components.