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The Exotic Absorption Peaks in One-dimension Phononic Crystals with Defect Mode

Author: XuHongMei
Tutor: YiLin
School: Huazhong University of Science and Technology
Course: Optics
Keywords: phononic crystals transfer method absorption factor high absorption surfacewave Tamm mode cavity resonant mode
CLC: O735
Type: Master's thesis
Year: 2012
Downloads: 7
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Abstract


Acoustic absorption has been one of hot topics in home and abroad, it plays asignificant role in the preparation of acoustic functional materials and engineer applications,for example noise control and ultrasonic detection. Many explorations about the so-called“dark” acoustic materials have also attracted researcher’ attention, which can reached closeto100%absorption of incident acoustic waves in some frequencies region, according toreports, one kind of structure for acoustic absorber is composed by a dissipative corewrapped by a gradient index shell. The shell guides the acoustic waves towards the centerand the core dissipates the energy, thus, this model can obtain omnidirectional broadbandacoustic absorption, application prospect is very comprehensive. The article make apreliminary exploration for the basic properties of the absorption in a one dimensionphononic crystals, the content of the whole article as followed.In this letter, firstly, we study an beam of acoustic wave incident normally through aone-dimensional period (10periods) phononic crystals (PCs) consist of two kinds ofmaterials by transfer method, dissipation has been considered by adding a complex constantabsorption factor on the lame constants of components. Subsequently, the transmittalproperty (transmission&reflectivity) depend on the loss factor has been discussed.Secondly, we study acoustic wave incident normally a specific1-D layered phononiccrystals. At the condition of only0.1%absorption factor has been added.99.7%highabsorption of the incident acoustic wave can be achieved. It owes to the excitation of surfacewave at the boundary between the last layer and emergent material. In addition, we analyzethese factors which influence the frequency and magnitude of absorption peaks, in a conclusion: if choosing materials correctly and designing the structure reasonably, exoticabsorption peaks can be obtained. Moreover, this mode has advantage of unidirectionalproperty and stability.Lastly, another1-D layered phononic crystals has been proposed, which also realizedapproximately100%perfect absorption. While it dues to the excitation of Tamm mode andcavity resonant mode respectively, by analyzing the field displacement, we distinguishcharacteristics and forming-mechanism respectively of two modes, meanwhile, we concludethe influence factors for the frequency and magnitude of absorption peaks, for the purpose offlexible and efficient control for absorption.

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CLC: > Mathematical sciences and chemical > Crystallography > Crystal physics > The acoustic properties of the crystal
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