Abstract: There has been a growing interest in recent years in the study of man-made two-dimensional periodic structures of dielectric materials known as “photonic crystals.” A major reason for this is the fact that these systems exhibit forbidden frequency bands (photonic band gaps) extending throughout the Brillouin zone. In these regions, electromagnetic waves are absent along all directions since they are strongly reflected by the structure. The existence of band gaps can lead to numerous practical interests such as DWDM in the optical communication application.
The analogy between photons and phonons suggests that band gaps would also be found in the systems comprised of two materials with different elastic properties called “phononic crystals.” Acoustic waves propagating in such structures also exhibit band gaps and may find applications in the high frequency acoustic wave devices.
The purpose of this proposal is to elucidate theoretically and experimentally the characteristics of surface acoustic waves in 2D phononic crystals with fully accounts of the elastic anisotropy of both the cylindrical filler and background material. In the theoretical part, band gaps will be studied using the plane-wave expansion method, which is composed of the Bloch’s theorem and the reciprocal lattice vectors. The cases of surface acoustic waves of anisotropic materials in square and hexagonal lattices will be examined in particular. In the experimental part, high frequency SAW device will be designed and fabricated to generate broadband surface waves propagating in a 2D phononic structure with silicon as the background material. Standard MEMS process such as Reactive Ionic Etching (RIE) technique will be employed to fabricate a two dimensional phononic structure with square lattice arrangement.
surface acoustic waves