Investigation On Amplitude And Phase Manipulation Technology Of Electromagnetic Wave Based On Metasurfaces

Metasurface is a kind of subwavelength artificial electromagnetic structure with feature dimensions smaller than the operation wavelength.By properly aligning the arrangement of the unit cells and selecting the composed materials,metasurfaces can achieve exotic electromagnetic responses that can hardly be realized by natural materials and traditional compound materials.Thus,metasurface has opened a new door for controlling the electromagnetic waves and has drawn widely attentions in the fields of electromagnetics,optics and photonics.Current investigations have shown that due to its high integration,multi-functionality and lightweight features,metasurface has unique advantages for communication,holography,sensing and imaging.In recent years,although the researches on metasurface has achieved preliminary results,this field still lacks universal design theories and the physical mechanism of the interaction between electromagnetic wave and metasurface is not fully clear.Thus,how to further improve its working efficiency and bandwidth is a key problem remained to be solved.Based on the two most basic parameters of electromagnetic waves,amplitude and phase,this thesis carried out the researches on amplitude and phase modulation technologies of electromagnetic waves based on metasurfaces.The purpose of this thesis is to further improve the working efficiency and bandwidth of the metasurface without the sacrifice of its inherent advantages.The main works are listed below:1.In order to enrich the design theories in the field of metasurface,by analyzing the electric field and impedance distribution in a certain kind of metasurface based on the basic electromagnetic theory,this thesis developed the catenary electromagnetic models.This mathematical model can accurately describe the electromagnetic performance of metasurface,which laid the foundation for the design of subsequent devices.2.Aiming at the problems that current metasurface cannot achieve highly efficient amplitude modulation and has narrow bandwidth,this thesis has proposed various metasurfaces for broadband amplitude control based on different theories such as transfer matrix method,effective media theory,dispersion control method and catenary electromagnetics.Both simulated and measured results demonstrated that the proposed devices showed great advances over their traditional counterparts.3.In order to achieve broadband phase modulation,this thesis proposed a novel method by employing the non-linear phase response based on catenary electromagnetics.As a proof of concept,broadband cloak and antenna has been designed and characterized in microwave region.Compared with previously reported devices,the proposed devices have broadened bandwidth and similar gain.4.By employing the intrinsic polarization properties of electromagnetic waves combined with the anisotropic response of metasurface,this thesis proposed two kinds of functional devices that can achieve high performance amplitude or phase modulation under different polarized incidence respectively.By properly selecting the polarization of incident waves,the amplitude-modulated metasurface can realize circular and linear dichroism,while the phase-modulated device can generate self-accelerating beams with different trajectories.