Research On Terahertz Cloaking Structures Based On Metasurface

In general,terahertz refers to electromagnetic wave with a frequency of 0.1 THz ~10 THz.The discovery of metamaterial and metasurface provides a material basis for the researches and applications of terahertz waves.This paper mainly studies the terahertz metasurface cloaking structures based on three types of electromagnetic cloaking theories,including:(1)Broadband absorbers based on metasurface.According to the resonant properties of metasurface,absorbers can be divided into electromagnetic resonance absorbers and circuit resonance absorbers.Generally,broadband absorption performance comes from the overlap of absorption peaks of multiple subunits or the adoption of multi-layer structures.According to this,we designed a composite wideband absorber composed of several resonators and a multi-layer wideband absorber respectively,and both of them can be used in terahertz cloaking.(2)Ultrathin cloaking carpet based on generalized Snell's law.According to the generalized Snell's law,the phase discontinuity of the electromagnetic wave at the dielectric interface can be controlled by designing phases of the metasurface elements.This paper designed a terahertz ultrathin triangle cloaking carpet,and when the electromagnetic wave of 0.84 THz shotting to the carpet by an incident angle 45 °,the electromagnetic wave reflected directly due to the phase compensation which achieving cloaking.(3)Metasurface-based linear polarization and circular polarization cloaking structures.For line-polarized waves,cloaking is achieved by converting detection waves into their coherent polarization.The polarization conversion rate of the designed line-polarized converter is more than 95% at 13.1THz~20THz.In addition,based on the linear relationship between the rotation angles of the optical axis of the metasurface units and the spatial reflection phases when the circularly polarized wave is incident,a planar wave deflection device and a triangular ultrathin cloaking carpet are designed,which can achieve cloaking when circular polarization wave is incident.The cloaking structures and design methods in this paper can be selected according to the actual application environment and the requirements of cloaking materials,which has certain reference value.