The Researches On Basic Theory And Transmission Characteristics Of The Topological Phononic Devices

In recent years,the demand for acoustic communication and acoustic detection in special situations has been strong and rapid.However,there are some limitations: the characteristics of traditional acoustic materials in acoustic communication devices limit the ways in which sound waves can be regulated.Nowadays,the application of topological materials in acoustic integrated devices has made great progress and has become the focus of many researchers.The main benefit from the topology of materials in a variety of dispersion relations and peculiar characteristics,through the purposeful design of artificial crystal band structure,realize the sound waves in artificial crystal high local,broadband,multi-band frequency and low loss of energy transmission,there is no doubt that in manufacturing or basic research way to have more control in such aspects as sound waves.Based on the two-dimensional topological phononic crystal structure,this thesis designs two kinds of acoustic communication devices which can realize the broadband and dual-band.The k · p perturbation theory is used to realize the one-way propagation of acoustic waves in the air to suppress the backscattering,and the simulation proves that the designed topological phononic crystal has strong robustness.Specific contents are as follows:1)A compound phononic crystal structure in the form of a hexagonal lattice composed of two artificial atoms is proposed.The band of phononic crystal,namely the dispersion relation,is obtained by numerical simulation using the compound structure device to achieve the purpose of broadband(relative bandwidth is 22%).By adjusting the area of adjacent atoms,the degeneracy is broken,and the relative position is changed to produce the band inversion,and the topological phase transformation is realized.On this basis,combining two topologically different structures,the edge state with pseudo-spin correlation is simulated.Finally,it is verified that this edge state possesses the characteristics of backscatter suppression and one-way transmission.2)A graphene-like honeycomb-shaped two-dimensional phononic crystal structure device is proposed.With air as the matrix and acoustic rigid material as the scatterer.Two linear Dirac degenerate points exist at the K point in the Brillouin region,which improves the acoustic communication channel and realizes the sound transmission in two frequency bands.And we also used finite element simulation software to calculate the energy band of the two-dimensional honeycomb phononic crystal,used two different topological structures to verify that the edge states that can suppress backscattering is generated at the interface of the two structures,and further explore the edge states strong robustness against sharp bends and defects.Finally,due to the edge states possesses the characteristics of one-way transmission,the dual-channel beam splitter function is realized.