Research On Polarization Converter Based On Metamaterials And Its Electromagnetic Characteristics

Electromagnetic metamaterial is a periodic structure that can be designed artificially and flexibly.The particular electromagnetic property can be obtained by designing the different unit structure.Phosphorene,as a new graphene-like single-atom thickness two-dimensional material,has the characteristics of in-plane anisotropy due to its unique atomic arrangement,which provides a novel idea for the design of metamaterial.In this paper,based on metal and phosphorene metamaterial,several kinds of transmission and reflection polarization converters are proposed and investigated.The main contents of this work are as follows:(1)Based on metal metamaterial,two cross-polarization converters operating in multiband and transmission mode are designed.The first converter is composed of two layers with orthorhombic grating structure and two layers with double cross asymmetric metal metamaterial.It operates in the frequency ranges of 0.99 THz-1.09 THz,1.10 THz-1.30 THz,1.40 THz-1.51 THz,and 1.60 THz-1.65 THz.In the operating frequency band,the incident linearly polarized wave can be efficiency converted into a cross-polarization transmitted wave.The conversion mechanism of the cross-polarization converter is analyzed by using the surface current distribution.The second converter is designed based on the metal structure with the “WIFI signal” shape.The upper and lower layers of the structure are orthogonal gratings,and the middle layer is a structure with the “WIFI signal” shape.The operating frequency bands are 0.26 THz-037 THz,0.42 THz-0.47 THz,0.63 THz-0.65 THz,and 0.68 THz-0.74 THz.The polarization conversion performance is investigated by the sweep of parameters.(2)Based on metal and phosphorene metamaterials,two reflective polarization converters are proposed and investigated.The first one is the reflective cross-polarization converter with the “WIFI signal” shaped metal metamaterial.The upper layer is a “WIFI signal” shape metal microstrip structure,the lower layer is a reflective metal ground,and the middle layer is a dielectric material.This converter operates in the frequency ranges of 0.32 THz-0.39 THz,0.49 THz-0.60 THz,and 0.71 THz-0.78 THz.The second one is a phosphorene-based metamaterial reflective linear-to-circular polarization converter.Based on phosphorene metamaterial,we propose a broadband reflective linear-to-circular(LTC)polarization converter in a mid-infrared regime.The proposed converter consists of periodic unit cells,each cell of which is formed by multiple phosphorene layers,a dielectric layer,and a fully reflective gold mirror.The optimal polarization conversion performance is obtained by the sweep of parameters.The operating frequency bands is 12.82 THz – 23.28 THz.The simulation results show that the relative bandwidth of LTC polarization conversion reaches 58% and 47.8%,respectively,when the pucker ridge alignment(PRA)of the phosphorene perpendicular to y-direction and x-direction.Finally,the conversion mechanism of the polarization converter is analyzed by using the current distribution and equivalent dipole resonance theory.