聲子晶體為兩種或兩種以上的材料經過週期性排列組合而成，由於其週期性關係對於波傳行為會產生頻隙現象，不論是固體中的應力波或是空氣的聲波皆會產生此現象。若將其週期性破壞會使結構形成缺陷，常見的缺陷有點缺陷以及線缺陷。點缺陷即為常見的聲子晶體共振腔，而聲子晶體波導即利用線缺陷形成。聲子晶體除了於頻隙現象已有大量討論之外，尚有在傳導區內擁有異常之頻散現象，如負折射特性，這些特性對於往後元件設計上能有更進一步的改良以及進步，因此使得該方面之研究成為最近學術界的熱門話題。
本文首先利用平面波展開法以及有限元素法求得聲子晶體之色散曲線圖，進而結合超晶胞法得到聲子晶體波導之色散曲線圖以預測波導間的耦合現象，如能量完全傳遞之頻率、耦合長度等等。一般而言，當兩條波導在一定的距離之下，會產生耦合之現象，即兩條波導之間的距離接近到一定距離之內，模態便會互相影響。當波導結構與其表面波導結構進行耦合，會產生聲學表面波之現象，並藉由改變表面波導結構透過色散曲線之關係進而探討其不同表面波之性質。以往聲學表面波大部分用指叉電極結合壓電材料來激發，這樣的聲子晶體結構能夠為科技業帶來不一樣的思維。

Phononic crystals are periodically composed of two or more materials, regardless of the elastic waves in solids or sound waves, band gap phenomenon are generated due to the cyclical relationship for the wave propagation. Destruction will make periodic structure to the defect formations, common defects are point defect and line defect. Point defect is the common phononic crystal resonant cavity, while the phononic crystal waveguide that is, the line defect. Phononic crystals have a lot of discussion to the frequency gap phenomenon. In addition, there has abnormal dispersion phenomenon in the propagation area, such as negative refraction characteristics of these features for further improvement and progress on the design of subsequent components. Thus, this aspect of the study becomes a hot topic of recent academia.
Firstly, using the plane wave expansion method and finite element method to obtain phononic crystal dispersion curves, and then combined with the supercell method to get dispersion curve of phononic crystal waveguide to predict the coupling between the waveguide, such as energy pass, coupling length and so on. In general, the coupling phenomenon occurs when the two waveguides between certain distance. Namely, the distance between the two waveguides are close, the mode will affect each other. Coupling between waveguide structure and the surface of waveguide produced the acoustic surface wave phenomena, and discussing the relationship between surface waveguide structure and surface wave behavior. In the past, most of the acoustic surface wave excited by interdigital electrodes combined with piezoelectric material, via this novel phononic crystal structure would bring the different thinking for the technology industry.

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