Research On Transmission Properties Of Photonic/Sonic Crystal Based On Artificial Unit Cell With Anisotropic Constitutive Parameters

Photonic crystals,which can be used to control the propagation of electromagnetic waves by virtue of special spatial symmetry,are vividly called“semiconductors of light”.Most of the present photonic crystals are arranged in array by isotropic medium based unit cells with simple electromagnetic parameters.Metamaterials can provide more diverse constitutive parameters by designing the unit cells at the subwavelength scale,and hence opens a new degree of freedom for electromagnetic manipulation.In this thesis,artificial unit cells with anisotropic or even bi-anisotropic constitutive parameters were introduced into photonic crystal design to explore the phenomenal electromagnetic transmission in this crystal,and this idea was extended to acoustic communities for acoustic manipulation.The results are as follows:Firstly,a topological photonic crystal supporting pseudospin edge waves was constructed by introducing the bi-anisotropy effect into a planar waveguide photonic crystal.The photonic crystal was arranged in a square array and possesses accidental degenerate ring in the band structure.A complete band gap with non-trivial topological properties,which was verified by non-zero Z₂ invariant,was formed after introducing bianisotropic effect by adding air gap into the waveguide.Simulation results demonstrate that the topological photonic crystal supports pseudospin edge waves which shows remarkable robustness to the sharp bent and disorder perturbation.In addition,a three-dimensional topological photonic crystal based on split-ring resonators was proposed,which can support spin-momentum locking surface modes.Furthermore,a two-dimensional deformed photonic crystal operating in transverse magnetic modes was studied to explore the band structure and propagation characteristics of pseudospin edge waves supported by the crystal.The results will contribute to the study of photonic topological waveguides and pseudospin photonics.Based on the aforesaid study,the concept of anisotropy was applied to the design of one-dimensional sonic crystals to realize broadband extraordinary acoustic transmission.Acoustic wave traveling through a surface with subwavelength holes shows extraordinary transmission at specific wavelength.Present resonance-enhanced transmission structures have strict limitation on the wavelength and are hard to realize broadband transmission.To solve this problem,a one-dimensional sonic crystal was proposed with anisotropic-density unit cells which support multiple acoustic resonances within a certain bandwidth.Multiple-scattering-model analysis and experimental tests manifest that the sonic crystal supports broadband extraordinary transmission of incident plane wave.This structure contains potential application value in acoustic transparent devices.