缺陷型表面声子晶体对声波的调控

发布时间：2018-08-01 08:50

【摘要】：声子晶体丰富的物理内涵激发了大家的研究兴趣,其丰富可调的色散关系使声波在声子晶体中具有多种独特的传播方式。本文对结构声表面波在表面声子晶体中的操控进行研究,我们知道结构声表面波作为一种新型的表面波,近年来得到学术界的广泛关注,它不仅具有表面波的特性,同时还具有自身的优势,许多表面波的物理现象都可以通过对结构声表面波的测量和分析进行研究。文中关于结构声表面波的研究对多功能集成声学器件的设计具有一定指导意义。本文主要从以下几个方面开展工作:首先,研究结构声表面波的色散关系受几何参数的影响,发现在刚性板上刻较宽和较深的凹槽能得到局域性更好的结构声表面波。我们设计了刻有周期性凹槽的三维刚性板,得到了非常平坦的结构声表面波等频色散线,利用等频色散线的独特形状实现了结构声表面波的自准直传输,这将对于新型声学器件的设计提供一定的理论指导。其次,通过一个45°楔型表面声子晶体可以实现结构声表面波的直角转弯及成像,所成像的半高宽为0.316λ。如若将两楔型声子晶体合并且引入一条线缺陷,则入射的准直波束会分为反射和透射两部分。反射和透射的能量比可通过缺陷大小任意调节。直角转弯机制和分波机制突破了自准直声信号只能沿直线传播的限制,将其推广为未来多功能复合声学器件中信号传输的一种有效手段,对于声学器件的集成化发展有一定的推动作用。最后,通过改变晶体中某一格点或某一排格点的几何参数可以构建点缺陷和线缺陷。利用有限元法与超胞法能够十分方便地计算出表面声子晶体的点缺陷和线缺陷对应的缺陷态带结构,以及特定频率的声波局域在点缺陷与线缺陷的本征压力场图。基于缺陷态的分析,我们实现了表面结构声波导。此外,研究的自准直声束在不同平面的转弯则是将结构声表面波从二维结构表面拓展到三维空间传输。
[Abstract]:The rich physical connotation of phonon crystals has aroused the interest of the research, and its rich and adjustable dispersion relationship makes acoustic waves have a variety of unique modes of propagation in phononic crystals. In this paper, the manipulation of structural surface acoustic waves in surface phonon crystals is studied. We know that structural surface acoustic waves, as a new type of surface waves, have attracted extensive attention in recent years, and they not only have the characteristics of surface waves. At the same time, it has its own advantages, many of the physical phenomena of surface waves can be studied through the measurement and analysis of structural surface acoustic waves. In this paper, the study of structural surface acoustic wave has a certain guiding significance for the design of multifunctional integrated acoustic devices. The main work of this paper is as follows: firstly, the influence of geometric parameters on the dispersion of structural saw is studied. It is found that the wider and deeper grooves on rigid plates can obtain better localized structural surface acoustic waves. We design a three-dimensional rigid plate with periodic grooves, and obtain a very flat surface acoustic wave isofrequency dispersion line, and realize the self-collimation transmission of the structure surface acoustic wave by using the unique shape of the equal frequency dispersion line. This will provide some theoretical guidance for the design of new acoustic devices. Secondly, a 45 掳wedge-shaped surface phonon crystal can be used to realize the right-angle turn and imaging of the structural surface acoustic wave. The half-maximum width of the imaging is 0.316 位. If two wedge-shaped phonon crystals are combined and a line defect is introduced, the incident collimation beam will be divided into two parts: reflection and transmission. The energy ratio of reflection and transmission can be adjusted arbitrarily by defect size. The right-angle turning mechanism and the split-wave mechanism have broken through the restriction that the autocollimator acoustic signal can only propagate along the straight line, and it has been extended to be an effective means of signal transmission in the future multifunctional composite acoustic devices. It can promote the integrated development of acoustic devices. Finally, point defects and line defects can be constructed by changing the geometric parameters of a lattice or a row of lattice points in a crystal. The finite element method and the supercell method can be used to calculate the defect band structure of the point defect and the line defect of the surface phonon crystal and the intrinsic pressure field diagram of the acoustic wave localized at the point and line defect of the specific frequency. Based on the analysis of defect states, a surface structure acoustic waveguide is realized. In addition, the turning of the self-collimating sound beam in different plane is to extend the surface acoustic wave from the two-dimensional surface to the three-dimensional space.
【学位授予单位】：吉首大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O735

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