Continuous tuning of line defect modes in silicon two-dimensional phononic crystal

Abstract

In this paper, a methodology for continuous tuning of confined line defect modes in two-dimensional phononic crystal is demonstrated. In this work, different from the general method, where line defects are formed by removing several rows of cells from a perfect phononic structure, the line defect is considered as a free vibrating plate, and separated from the surrounding phononic structure. Thus, width of the line defect could be continuously adjusted. The simulated results show that, with this method, resonant frequency of the confined defect mode could be continuously modified, and precisely determined to keep it locating at the central part of the phononic band gaps. It is also illustrated that different resonant modes (i.e. flexural and extensional modes) have different relationships with the width of the line defect, and the unwanted resonant mode could be excluded from the phononic band gaps by carefully selecting the defect width. Further simulation results indicate that each defect mode has an optimal width, in which case quality factor of the defect mode is maximum.