Research On Anomalous Reflection Characteristics Of Optical Gradient Metasurfaces

Metamaterials have become research hotspots because of their properties that natural materials do not have,and the flexibility to design unit structures.However,with the further development of research,metamaterials were restricted by material loss and structural volume,and their practical applications had hindered.Metasurfaces were easier to manufacture and had lower losses,which have gradually become a new direction of research.Metasurfaces enable free regulation of light,among them,the anomalous reflection controlled by gradient metasurface reflect the ability of the metasurface to regulate incident light,and related researches have been rapidly developed.This thesis used the generalized Snell's law and the principle of Pancharatnam–Berry phase(PB phase) to design and study the gradient metasurface of silicon carbide(SiC) and gold materials.The researches mainly focused on the anomalous reflection characteristics of metasurfaces in different wavelength bands.At the same time,the related factors which have affected the efficiency of anomalous reflections were also studied.The specific works are as follow:1.In the far-infrared band,the gradient metasurfaces of SiC materials were designed,and their anomalous reflection characteristics were studied.The surface phonon polariton supported by SiC exhibited characteristics similar to those of metals.It has a negative dielectric constant and high reflectivity,which was convenient for designing anomalous reflection metasurfaces.The anomalous reflection efficiencies of three different SiC gradient meta surfaces were different.For different structures,the influence of parameter changes on the anomalous reflection efficiency and resonance frequency had been studied.The simulation results showed that the anomalous reflection efficiency of single-layer SiC gradient metasurface were 60%.The device of SiC metamaterials could be used in aspects of thermal radiation and anomalous reflection.2.In the near-infrared band,gradient metasurfaces of gold material had designed.Because the metal bar structure had a strong response to anisotropy,and the metal structure also had a very high cross-polarized reflection efficiency in the study of anomalous reflection,this thesis chose the gold bar as the unit structure of the gradient metasurfaces.The metasurface had double-layered gold structures.The difference of rotation angle between the upper and lower gold structures was used as a variable,and its influence on the anomalous reflection was studied in the double-layered gold structures.The asymmetric reflection of the gold bar and gold slot composite structure was studied,and analyzed the effect of thickness difference on the asymmetric reflection.