Design And Research Of Micro Devices Based On Terahertz Metasurface

In recent years,with the rapid development of 5G communication technology,terahertz has attracted more and more attention due to its superior characteristics.In the electromagnetic spectrum,terahertz lies between microwave and infrared ranges,as a macro to micro photonic electronics transition region,its low photon energy,high penetration,high resolution.Terahertz waves also have great application prospects of remote sensing,high-speed communications,public security,biological medicine.In terahertz applications,terahertz wavefront regulation also plays an important role.However,terahertz applications are limited due to the weak interaction with natural materials,the large volume,and low efficiency of traditional terahertz devices.And then,the appearance of electromagnetic metamaterials has made up for some shortcomings of natural materials.However,at micro/nano scale,metamaterials have disadvantages such as high loss and difficulty in three-dimensional manufacturing,which make it difficult to apply metamaterials.Later,the emergence of a two-dimensional metamaterial with subwavelength thickness,called the metasurface,provides a new way to regulate electromagnetic waves.Compared with 3d metamaterials,2d metasurfaces have the advantages of small volume,easy manufacturing and low loss.Therefore,metasurfaces can replace largevolume 3D metamaterials in many application fields and have greater development space.This paper mainly focuses on the study of wave front regulation of terahertz by metasurfaces.The main contents of this paper are as follows:(1)The research background and significance of terahertz and metasurface are introduced.And the recent literature is reviewed and the structure of this paper is discussed.(2)The generalized Snell’ laws,the principle of metasurface phase control: transmission phase control and geometric phase control,the methods used in scientific research in this paper,the finite difference time domain method,and softwares CST Microwave Studio and FDTD Solutions based on this method are introduced.(3)Based on the transmission phase theory,a silicon rod metasurface with vortex-focusing property is designed.All-silicon metasurface can realize flexible full-vector manipulations of complex optical field,without confronting the loss issues of plasmonic counterparts,and thus have been proposed for lots of nano-photonic functionalities.In this work,a silicon-bar metasurface is designed with optical-vortex focusing characteristic,which is duplexed for orthogonal linearly-polarized terahertz waves.It achieves full phase modulation by tuning the lateral sizes of bar without anisotropic orientation requirement associated with the geometric phase,which is consequently of high efficiency since no polarization conversion is involved in.(4)Based on the geometric phase theory,a reflective wideband metasurface is designed.Its unit structure can realize polarization conversion in a wide band.Through the arrangement of the unit structure,polarization conversion can be realized,one-dimensional focusing,twodimensional focusing,abnormal refraction and vortex generation.(5)Summarize and forecast the whole paper.