利用聲子晶體探討點缺陷與共振腔波導現象

我們利用破壞完美聲子晶體的週期排列讓其能隙範圍產生缺陷頻帶，利用此種缺陷頻帶去侷限聲波或彈性波傳遞方向。此篇首先討論點缺陷在不同填充率與缺陷外部層數下，在缺陷頻帶頻率中共振腔內部壓力分佈情況，再來結合點缺陷包覆能量特性與線缺陷侷限波傳方向特性，形成三種排列方式雙L型、斜向排列與Y型進行討論。模擬方面我們主要利用有限元素分析軟體COMSOL計算出聲子晶體的能隙區域，因為缺陷頻帶將發生在能隙區域中，而缺陷頻帶又可視為傳導帶，所以我們在聲子晶體內製造不同的缺陷排列型態去分析這些缺陷對於濾波和波傳的影響，實作方面則是設計一組直徑 6mm鋁棒背景為空氣，填充率0.46，正方晶格排列之聲子晶體來進行實驗，模擬與實作結果發現，含有點缺陷聲子晶體可將能量集中侷限於缺陷中，產生共振現象。波導部分，斜向線缺陷波傳效果較為優異，因為點缺陷連續出現的緣故，在波導的路徑上發生連續性局部共振現象，因此能將能量集中傳遞，大幅提升波導效果。

關鍵字

聲子晶體；共振腔；波導

並列摘要

The disruption of the periodic alignment of perfect phononic crystals was introduced to create defective mode around the crevices. This defective mode was used to confine the progressive direction of sound wave or elastic wave. Three alignments, double-L and diagonal alignments, were investigated, and the characteristics of diagonal alignment was used to explore Y-splitter and combiner. For simulation, the finite element based program COMSOL was adopted to calculate the stopband of the phononic crystals. Various defective alignment modes were created in the crystals for the analysis of the influence of these defects on wave filtering and wave transmission. For practice, a group of aluminum bars with a diameter of 6mm and air as the background was designed at a fill rate of 0.46. Phononic crystals of square lattice were used for experiment. Finally, the results from simulation and experiment were compared, we can discover that the point defects can concentrate and limit the energy in the defects, and produce the resonance effect. In the waveguide part, the diagonal alignments defects is better than the double-L. The point defects appeared continuously, and in the path of wave guide occurred continuously partial resonance effect. Thus, it can concentrate the energy and then transfer. As the result, we can improve the waveguide effect significantly.

並列關鍵字

Phononic Crystal ； Resonant Cavity ； Waveguide

參考文獻

[1] C. Qiu, X. Zhang, and Z. Liu, “Far-field imaging of acoustic waves by a two-dimensional sonic crystal”, Phys. Rev. B Vol. 71, No. 5, 054302 (2005)

[2] J. Li, Z. Liu, and C. Qiu, “Negative refraction imaging of acoustic waves by a two-dimensional three-component phononic crystal”, Phys. Rev. B Vol. 73, No. 5, 054302 (2006)

[3] M. Torres, and F. R. Montero de Espinosa, “Ultrasonic band gaps and negative refraction”, Ultrasonics Vol. 42, No. 1-9, pp. 787-790 (2004)

[4] X. Zhang, and Z. Liu,“Negative refraction of acoustic waves in two-dimensional phononic crystals”, Appl. Phys. Lett. Vol. 85, No. 2, pp. 341-343 (2004)

[6] M. Ke, Z. Liu, C. Qiu, W. Wang, J. Shi, W. Wen and P. Sheng, “Negative-refraction 111 imaging with two-dimensional phononic crystals”, Phys. Rev. B Vol. 72, No. 6, 064306 (2005)

國際替代計量

利用聲子晶體探討點缺陷與共振腔波導現象

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