Electromagnetic Propagation Properties Of Artificial Microstructures

Through the design of sub wavelength artificial microstructures, the realization of the fantastic characteristics of artificial materials, such as negative refraction materials, zero refraction materials, gradient materials, has become a hot research topic in the last decade.Among them, the zero index material, the metasurface and the bi-anisotropic material are three important branches and directions in the study of artificial microstructures. As widely confirmed, they possess wide ranges of potential applications in industry and daily life.Starting from a brief review of the research progress of artificial microstructure, these three branches are discussed in this thesis. Firstly, the effects of a perfect electric conductor(PEC) defect on the transmission properties of zero index materials are investigated. We use dielectric photonic crystals with Dirac dispersion to realize the double zero-index material. We find that the transmittance of this kind of material can be tuned by the size of the PEC defect. Therefore, some novel methods to control the transmission through a waveguide filled with zero refractive index material are proposed.Secondly, in order to study bi-anisotropic materials, we develop an experimental method to measure the effective electromagnetic parameters. By measuring all of the scattering matrix parameters(S-parameters), multiple electromagnetic parameters of bi-anisotropic materials can be obtained. Based on this method, we also design a unit cell of bi-anisotropic microstructure with the shape of "卍". Through the analysis of simulation results of the current distribution on the microstructure with the shape of "卍", we discuss the physical mechanism of the internal electromagnetic coupling.Finally, we design a metasurface, through which reflection based focusing effect can be realized and is independent of the incident light polarization. The focusing effect isverified by our microwave experiments and good consistence between simulations and experiments can be found.By all these works, artificial microstructures have been explored and I hope that our study will benefit to industry and daily life.