Research And Application Of Reflection Efficiency Of Metasurfaces

Since metasurfaces are proposed, the applications based on their different reflection efficiencies or transmission efficiencies have been required rapid development. Moreover, reflection type metasurfaces are also applied widely in various areas due to its interesting advantages, such as low volume and mass, sophisticated fabrication technology. In this dissertation, reflection type metasurfaces with different reflection efficiencies are researched and investigated intensively. Furthermore, the applications of metasurfaces reflectarray are extended by combining with the reflection phase.In chapter 1, the research background and significance of this dissertation are introduced. In addition, the artificial composite materials are defined based on their different electromagnetic characteristics. Then, the origin, development history and current advancement of metasurfaces are also reviewed. Finally, the main works and arrangement of this dissertation are outlined.In chapter 2, four kinds of methodologies to investigate the reflection efficiencies of metasurfaces are presented. Then, their advantages and disadvantages are introduced. In addition, an equivalent circuit of the metasurface composed of dual-loop structures array are proposed and investigated, which provides an important reference and guideline to design metasurfaces with different reflection efficiencies in the next chapter.In chapter 3, two metasurface applications with different reflection efficiencies by tuning the dimensional parameters of the dual-loop structures, a metasurface absorber with low reflection efficiency and a metasurface reflectarray with high reflection efficiency, are proposed and researched in THz band. The metasurface absorber possesses polarization independence and keeps a good performance under wide-angle oblique incidence. Meanwhile, the metasurface reflectarray could present a high antenna efficiency at THz frequency. Finally, the corresponding samples are fabricated and measured. Moreover, factors which directly influence reflectivity and resonant frequencies caused by the fabrication process for THz applications are identified, which provides an important guideline to fabricate and measure other kinds of THz devices.In chapter 4, a metasurface reflectarray with the function of modulating the orbital angular momentum of the electromagnetic waves are proposed. The unit cell with three resonant structures, dual-loop and a dipole structures, can achieve a linear reflection phase curves in wide band. Then, two kinds of 20×20 metasurface reflectarray employed this unit cell is designed, fabricated and measured. The metasurface reflectarray successfully realize the orbital angular momentum mode of 1 and 2, which could increases the spectrum efficiency of electromagnetic waves effectively.In chapter 5, the research works of this dissertation are summarized and the future works are predicted.