Research On The Control Of Acoustic Wave By Two-Dimensional Sonic Crystals

In recent years, there has been growing interest in the sonic crystals (SCs) for theirrich physics and potential applications. Various unique spreading ways of acousticwaves in SC are determined by their dispersion relationships. A low loss of energytransport of sonic waves in a wide frequency range by SCs can be achieved by properlydesign of their band structure, which finds its application prospect in integratedacoustics. In this dissertation, control of acoustic waves by sonic crystals and novelapplications based on this controllability are investigated. The motivation for this studyis to provide some guidelines for design and fabrication novel acoustic devices. Themain work is included as follows:Firstly, we make a detailed analysis and research on the self-collimation of sonicwaves in two-dimension SC. The self-collimation principle is analyzed based ondispersion relationships of SC. The simulation results show that low lossself-collimation wave has been transport with a wide frequency coverage intwo-dimension SC as a two-dimensional SC composed of rubber-coated tungsten rodsarranged as a square lattice in water has a long flat equi-frequency contour (EFC) in awide frequency range. Then self-collimation effect for Gauss beam and point source arerealized in this two-dimensional SC, and a directional transmission is also achievedbased on the effect.Secondly, we make a systematic research on the sharp bending of self-collimationand subwavelength imaging of acoustic waves in two-dimensional SC. We introduceinto SC a truncation along ΓX direction. A total internal reflection of self-collimatedwaves is observed at the interface between sonic crystal and water, thus a sharp bendingoccurs when the sonic wave propagate along ΓM to the interface. A subwavelengthimaging with sharp bending is also observed due to the combined result of the totalinternal reflection and the very flat EFC that can transport both propagating andevanescent modes of the point source.Finally, we realize the split of self-collimation waves and subwavelength imagingof a point source by the introducing of defect modes in SC. We designed a1×Nbeamsplitter by this defect mechanism and investigated the splitter efficiency under deferentdefect modes and frequency. Such a splitter effect works well in the frequency range ofself-collimation.