Angular-dispersive Metasurface For Angular Manipulation Of Electromagnetic Scattering

Driven by a new revolution in technology and industry,electromagnetic devices play a vital role in 5G/6G communication technology,quantum computation,aerospace and other fields.The increasingly complex electromagnetic environment poses challenge to the performance of the devices,which put forward higher requirements for the devices,such as anti-interference,high efficiency and so on.However,the application of the traditional devices is strongly limited due to the lack of functionalities,low efficiency and low space-utilization rate.The manipulation of electromagnetic wave exploited by metamaterial/metasurface,stimulates huge interest among researchers and leads to the development of new technology,new materials and new devices.Angular-dispersive metasurfaces,which take advantage of the spatial dimension,can achieve many nontrivial angle-dependent functionalities and offer new possibilities for designing compact,functional and efficient devices.In this thesis,the manipulation of metasurface’s angular spectrum based on the angular-dispersive effect is investigated.An angular filtering metasurface based on the magnetic metamirror,broadband angular asymmetric scattering metasurfaces based on the anisotropic metagrating and broadband angular manipulated metasurfaces based on anisotropic medium are proposed and verified by the experiments.The thesis provides theories and methods for the design of angular-dispersive metasurface,which shows great potential for directional high-efficient transmission in complex environments.The contents of the thesis can be cataloged as follows:1.An angular filtering metasurface based on the magnetic metamirror is designed,which can achieve high-efficient band-stop filtering without extra signal noise.The mechanism of angle-selective absorption in bianisotropic metasurfaces is revealed,which implies a strong normal magnetic dipole resonance will be induced in the metasurface under oblique illumination.It is verified that the filtering width of the angular spectrum can be manipulated by changing the geometry parameters of the unit cell.Specifically,by introducing gain media,the angle-selective amplification can be realized.2.An angular asymmetric scattering metasurface based on the anisotropic metagrating is proposed,which can realize different high-efficient broadband manipulation of electromagnetic wave from two sides.A nontrivial phase modulation mechanism that breaks the efficiency and bandwidth limit is revealed.The time-reversed scattering channels can be suppressed by exploiting the mirror-symmetry-broken electric dipoles.An angular asymmetric phase retarder which can realize zero scattering and phase retardation and an angular asymmetric backscattering mirror which can realize zero scattering and high-efficient backscattering are theoretically studied and verified by the experiments.The design principle can be applied to terahertz,infrared and other higher frequency regimes.3.A broadband angular manipulated metasurface based on an anisotropic metasurface medium is proposed,which can realize symmetric and asymmetric angular scattering.Broadband symmetric angular manipulation is achieved by utilizing a uniaxial medium with an optical angle of 0? and a perfect electric conductor.Furthermore,high-stop and band-stop filters are achieved by adjusting the geometry parameters and dielectric loss.By utilizing a uniaxial medium with an oblique optical axis,an asymmetric angular device is proposed which can realize zero scattering and high-efficient absorption.