Control Of Polarization And Transmission Of Electromagnetic Wave Based On Metasurface

One of the hot topics in modern photonics is using artificial structures to control electromagnetic wave.As one of the basic elements of electromagnetic wave,polarization is very important in a variety of applications.Therefore manipulation of the polarization of light is a significant technology of modern photonics.At present,the research of two-dimensional metamaterials,which is called metasurface,is very popular with researchers.This is because the fabrication process of the metasurfaces is more simple than that of the stereomaterials.Which is more important is that the design flexibility and complexity of metasurfaces are able to meet the optical application requirement of many fields.There is no doubt that it's very convenient to take advantage of metasurfaces for controlling polarization state of electromagnetic wave.That will be facilitated the manufacture and promotion.Metasurfaces is composed unit cells,arranged periodically along two directions.Symmetrical characteristic of unit cell can directly affect the form of transfer matrix and polarization conversion properties.Although the research on chiral metasurfaces has attracted more and more researchers' attention and in-depth study has been carried on,the design method of the polarization conversion based on unit cell's symmetry is still to be improved.This paper derives the transfer matrix of the corresponding basic symmetry forms using transfer matrix,based on the description of the Jones matrix of matasurfaces.The summary of unit cells' symmetry can be used to design specific metasurfaces.Based on the theoretical analysis,this paper designs several simple and effective metasurfaces to manipulate polarization states of incident wave.The main work are as follows:The fully symmetrical structure is studied,and we focus on the coupling effect between different modes when structure's symmetry is broken.Based on the coupled mode theory,we propose to introduce yttrium iron garnet in order to break the space translation symmetry and time reversal symmetry,which results in coherent interaction.By solving the coupled mode theory equation,one can get reflection or transmission coefficient.What's more,we can get the desired reflection spectrum through regulating the coefficient.According to the symmetry analysis,this paper presents a design of a simple L shaped double-layered chiral metasurface,in order to realize strong asymmetric transmission.It's can be used as linear polarization converter,switching linearly polarized light to its vertical polarization.We have deduced and analyzed several kinds of symmetric forms of the metasurface's unit cell,which can be utilized to realize optical activity.And two kinds of symmetry structures are specifically proposed and calculated by numerical simulation.The simulation results are in agreement with the prediction of the theory.This provides a good design idea for the polarization state control of the metasurfaces.The results of this study have a strong guiding significance in metasurface design with polarization control function and are also helpful to the study of resonance characteristics of unit cells and optical transmission spectra.