Study Of All-dielectric Magnetic Metasurface Based On Trapped Mode Excitation

Metamaterials have become one of the research hotspots of modern science because of their novel characteristics that surpass natural materials.They are widely used in various fields such as industry,military,and life.In particular,electromagnetic metamaterials have had a profound impact on technologies such as microelectronic,light-matter interaction,artificial magnetism,and new energy utilization.This article focused on artificial magnetic materials based on metasurfaces.In previous studies,artificial magnetic metasurfaces were mostly made of metal materials and constructed by the principle of plasmonic resonances,which inevitably increased losses and cannot work in high-frequency regions.At the same time,some researchers have proposed to use the alldielectric structure to optimize performance,but they all used the Mie-type resonance in these structures.Although the operating frequency was greatly increased,the quality factor and the field coupling effect had been greatly reduced.In order to solve this series of problems,this article proposed to use the trapped mode excitation based on all-dielectric metasurface to construct artificial magnetic structures.Firstly,this research started with Mie scattering theory and electromagnetic multipole expansion theory.With the help of these two theories,the scattering cross section of a spherical particle was written in the form of multipole contribution.The comparison of the two theories fully proved the correctness of the electromagnetic multipole expansion theory.That laid a theoretical and technical foundation for the subsequent study of non-spherical particles.Secondly,the single isolated particles making up the metasurfaces were studied.The electromagnetic properties of metasurfaces were largely determined by their unit cells,and the unit cells were composed of isolated particles.The isolated particle was studied through the electromagnetic multipole expansion theory and group theory.The reasons and characteristics of trapped mode excitation were analyzed.The one laid a structural foundation for the next research on metasurfaces.Then,a unit cell composed of four-particle clusters was designed.The four particles in the unit cell had different orientations.According to different structures corresponding to different point groups,a series of arrays were proposed.The trapped modes excitations were found in these arrays,and their electromagnetic responses were described,explained,and predicted using group theory.In addition,artificial magnetic responses were found at these trapped modes frequencies.The metasurfaces composed of all-dielectric particles was usually explained by Mie theory or electromagnetic multipole expansion theory.However,this paper proposed a new way to describe the trapped modes by using group theory,which greatly reduced the theoretical difficulty.Finally,an all-dielectric metasurface with both ferromagnetism and antiferromagnetism has been proposed.At different resonance frequencies,two trapped modes were excited in one structure,and exhibited antiferromagnetism and ferromagnetism under two responses,respectively.It has realized the artificial magnetic structure with low losses,and expanded to high frequency.In addition,the potential polarization conversion in this structure was discovered.In summary,this article started with the trapped modes excitation.And then an all-dielectric metasurface based on the trapped modes with both ferromagnetism and antiferromagnetism was proposed.In addition to numerical simulation,this paper also used experimental means to verify the simulation results.