Research On Electromagnetic Wave Manipulation Of All Dielectric Structures Based On Coupling Effect

Metamaterial has received a lot of attention since it was proposed and achieved remarkable achievement in millimeter-wave and microwave region.However,when the frequency increases,the strong dispersion and loss characteristics in the metal structure greatly restrict the practical application of metamaterial such as left-handed metamaterial in Terahertz band.All dielectric metamaterial provides a possibility to solve problems above.Based on the Mie resonance theory,the scattering characteristics of the media under the condition of the coupling strength between the dielectric blocks is studied.In order to build a new all dielectric metamaterial structure,the field transformation theory is introduced.The purpose of changing the constitutive parameters of all dielectric structure is achieved by constructing a position matrix for each position in a specific space,so as to lay a foundation for the regulation of electromagnetic wave impedance and polarization.Coupling is a key issue in the research of the electromagnetic response of the all dielectric structure.In this thesis,the resonant properties of a single diele ctric block are investigated.The electromagnetic response of the all dielectric structure under the Mie resonance is analyzed.By using the Mie theory and coupling theory,the coupling effect over the resonance frequency is brought in.The overall resonance frequency and the change of the resonance mode are obtained by stacking dielectric blocks of the same size and shape respectively in three directions : direction of the wave vector,direction of the electric field and direction of the magnetic field.Then,the coupling effect between high permittivity dielectric resonators and the effect on the electromagnetic response is revealed.A method for constructing left-handed metamaterials based on the coupling effect of all dielectric single resonators is proposed.Based on the practical application of all dielectric structure,by using the theory of field transformation,an all dielectric polarization converter is proposed by analyzing the permittivity and permeability distribution function required by constructing the target field distribution.The frequency controllability achieved by changing the structure parameters is under discussion.The proposed polarization torsion / converter can realize the polarization torsion of the linear-linear polarization,the left-right conversion of the circular polarization and the linear-circular polarization conversion.The polarization converter reverses with a conversion efficiency of 99.3%.The correctness and rationality of the proposed structure are verified through the simulation optimization,sample processing and experimental measurements.In view of absorption decreasing in high-power occasions,a design method to broaden the bandwidth based on dielectric absorber is proposed.Use different order Mie resonance mode to achieve widening bandwidth characteristics.Simulation results show that the relative bandwidth can be effectively broadened by using this method.The absorber can work normally under a large incident angle of 65 degrees.By using the principle of optical transformation,the traditional spherical Luneburg lens is compressed in one direction,and an all dielectric compressed Luneburg lens with coupling effect with two compressed shapes of slim and flat is proposed.Compressed lens in the direction of electromagnetic waves into the original thinning of the original thickness of 1/7,making the application more flexible,easier to process.By taking advantage of the discretization of the compressed Luneburg lens,the weight of the incident wave is accomplished.The experiment results show that the whole lens system has a good convergence effect on the incident electromagnetic wave and has a strong suppression effect on the side lobe,and can achieve positive and negative 36 degrees beam steering.This research deeply reveals the electromagnetic mechanism of the all dielectric metamaterial,come up with more methods on novel device design.It has instructional effect on better understanding all dielectric metamaterial and microwave or THz device design in the future.