Simulation Study On Electromagnetic Regulation Based On Metal Metasurface Materials

Metasurface is a new type of two-dimensional material that can effectively manipulate the phase,amplitude and polarization of electromagnetic waves in the subwavelength scale,which retains the unique electromagnetic properties of traditional metamaterials,and the electromagnetic adjustment in metasurface is realized on surfaces with the advantages of low loss,low profile,easy design and fabrication,etc.Metasurface is an ideal platform for regulating the structural optical field and achieving ultra-miniaturization and integration of optical devices,and has a wide range of applications in many fields such as singular optics,electromagnetic cloaking,beam shaping,polarization control,optical holography,wireless communication and intelligent sensing.In this paper,by using the time-domain finite difference method and other methods,we intensively investigate the electromagnetic control in metal metasurface structures under the framework of electromagnetic theory.This paper aims to enrich and improve the theoretical system of electromagnetic manipulation in metasurfaces and provide a theoretical basis and scientific basis for the future development of related photonic devices.The main contents of this paper are as follows.1、A spin Hall metalens with cylindrical lens focusing performance based on geometric phase was proposed.The metalens consists of an array of identical metallic nanopores in which the geometric phase of the holes varies in only one dimension.It was shown that when the geometric phase of metal holes includes only left circular polarization(LCP)or right circular polarization(RCP)components,the lens only forms a focusing line for LCP or RCP light.Owing to the extremely similar hyperbolic phase distribution at different wavelengths and focal lengths,the lens enables focusing over a wide spectral range of 550-900 nm and beyond the optical diffraction limit.When the geometrical phase of the metal hole includes both LCP and RCP light components,the lens can simultaneously focus both LCP light and RCP light in the spectral range of 550-900 nm.By adjusting the orientation angle of the metal hole,the transverse and longitudinal position of the spin-dependent focal line can be adjusted arbitrarily.In addition,the intensities of focal line can be controlled by adjusting the ratio of the LCP(or RCP)components in the geometric phase.2、A new method for multi-dimensional manipulating of photonic spin Hall effect in metal metasurfaces was proposed.Firstly,an array of periodic metal nanopores was constructed.Based on the characteristics of geometric phase,LCP and RCP have opposite phase gradients in the same dimension,they can make the light beams of different photon spin states propagate along different directions.The deflection directions of the LCP and RCP lights are determined by the number of holes in one period,hole spacing and incidence wavelength.Based on the above results,we construct metal metasurface based on geometrical phase.When the geometric phase of the metal hole contains only LCP(or RCP)components,the metasurface enables focusing only for LCP(or RCP)light.When the geometric phase of the metal hole contains both LCP and RCP components,metasurface can focus at different positions for the photons of different spin states.In other words,the spin Hall effect of photons is realized.Using this effect,we obtain the focusing of LCP and RCP lights at arbitrary positions in space.That is to say,we can independently control the transverse and longitudinal focusing positions of LCP and RCP lights.In addition,as the angle of incidence increases(less than 30°),the focal spot gradually deviates from the theoretical value,but maintains a good focusing performance.3、A simple and efficient polarization converter based on a reflective metasurface was designed.The polarization converter was composed of an array of different anisotropic cross-shaped metal particles.Using the anisotropic phase gradient in the plane,the metasurface can not only separate the electromagnetic waves with different polarization states,but also flexibly adjust the polarization states of electromagnetic waves,including converting linearly polarized light into LCP light or RCP light,and changing from circularly polarized light to linearly polarized light.The polarization converter greatly reduces the energy loss and achieves a polarization conversion efficiency of more than 88%。...