本研究對聲子晶體的拓撲邊緣模態、共振腔和缺陷模態做結合並應用於波長多工器，提出用作彈性波多工器的二維聲子晶體結構，設計的聲子晶體由樑中嵌入三角形質量塊組成，整體結構皆採用鋼，以此單位晶格為基礎作為多工器的基本結構。輸入波導採用的是拓樸邊緣模態之介面，利用破壞原本基本結構的空間反轉對稱性，使其產生僅在介面處傳遞的波導。此外還設計了共振腔，當輸入波導之能量為共振腔之共振頻率時，其能量會被共振腔擷取，共振腔是由超晶胞中的點缺陷製成的，本文設計方法為在去除一部份之結構後再另外加入一個圓柱體，利用改變圓柱半徑可以有效調整共振頻率。接著，還設計了可以與共振腔耦合的線缺陷輸出波導，使共振腔所擷取之能量能夠沿著輸出波導輸出至輸出端。以上述之方式首先建立一單通道結構，觀察其輸出端所接收能量之情形，再由單通道加以延伸至二、三、四通道，通過有限元分析軟件COMSOL Multiphysics®進行全波模擬，由模擬出之位移響應圖可以明顯看出皆在輸出端獲得共振腔的共振頻率。最後，設計另一結構，其輸入波導為與輸出波導相同的線缺陷，並與拓撲介面之波導進行比較，由兩者結果可觀察到，使用拓撲波導比線缺陷波導更好地擷取特定頻率。

This study introduces the two-dimensional phononic crystal structure that operates as an elastic wave demultiplexer. It combined by topological edge modes, resonant cavity, and defect modes of phononic crystals and apply them to wavelength demultiplexer. The designed phononic crystal is composed of an unit cell of the beam add with triangular mass. It will be the basic structure of the demultiplexer. The input waveguide structure breaks the space reversal symmetry of the basic structure, which only occurs at the interface between topologically inequivalent phononic crystals. Then the resonant cavity was designed to capture the resonance frequency from input waveguide. Cavity was made of a point defect in the super cell, also add a cylinder into it. Cylinder can adjust the resonance frequency by changing its radius. After manufacturing cavities, a line-defect output waveguide was designed to couple with cavity. The final structure in this thesis is a four-channel demultiplexer. It was analyzed by the finite element software COMSOL Multiphysics®, and studied its full-wave simulation. Obviously, it can respectively obtain every cavity’s resonance frequency at the output. Also, the line-defect input waveguide that same as output waveguide was designed. The structure’s result was compared with topological waveguide. To capture the specific resonance frequency, using topological waveguide is more accurate than line-defect waveguide.

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