Abstract: There has been a growing interest in recent years in studying the 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 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.
This proposal is a follow-up of the first year’s pre-study on the phononic surface acoustic wave’s bandgaps. For further investigation of phononic crystals with defects, in this proposal, we will develop a finite difference based computer code for studying the phononic bandgaps. In the first phase, to minimize the computation time in calculating the wave bandgaps in phononic structures, PC cluster will be implemented. The computer code based on the plane wave expansion method for solving the surface bandgap problems which is developing currently will be transformed into the form that is suitable for running in the PC cluster. For analyzing phononic bandgap in structure with defects, a finite difference based numerical code will be implemented; in addition, the absorption boundary condition will be studied. In the second phase, we are going to use the numerical code to study the wave propagation in phononic structure with sharp bend. In the experimental part, high frequency SAW device will be fabricated and integrated to the phononic crystal to study the bandgap characteristics. Finally, the experimental results will be compared with that of the numerical results, and the potential applications will be discussed.
surface acoustic waves