Research On Active Control Holography In Terahertz Regime Based On Vanadium Dioxide And Metasurface

Terahertz waves and relevant technology have become a new field of electromagnetic wave in recent years.They have attracted a large number of interests of researchers all over the world and the research on them is very popular.As a new favorite in the field of materials,metamaterials and metasurfaces have provided a large quantity of designs for functional device in terahertz region.They are different from the existing materials in nature as they can accomplish many complicated and unique functions by employing the well-designed unit structure.Based on the basic theory of metasurfaces and terahertz waves,an active control holography in terahertz region combined with metasurfaces and vanadium dioxide which is a kind of phase transformation material is studied in detail in this paper.The details are as follows:1.Background of this paper.First,we introduce the historic evolution,research status and application fields of terahertz theory and technology.Second,we present the history and characteristic of metamaterials and metasurfaces,as well as their advantages and application prospect when they are mentioned with terahertz theory and technology.Finally,we introduce unique characteristic of phase transformation in the vanadium dioxide and the mechanism inside it.2.The principle and calculation process of holography.Here,we firstly introduce the history of the development of the early holography.Second,we show the origin and main principle of computer generated holography(CGH).Then we introduce the advantage of metasurfaces when they act as the holograms in CGH.Next,we explain that different occasions need their suitable diffraction theories and these diffraction theories share the same essence.We also show two of them in this section.Finally,we present GS(Gerchberg-Saxton)algorithm which plays an important role in CGH.3.The research of active control holography in terahertz region based on vanadium dioxide and metasurface.Firstly,we present the numerical simulation software and experiment system used in our demonstration.We introduce the origin,development and basic function in the software and the construction and working mechanism of experiment system.Secondly,we show the design and the function of the unit structure of the active control hologram.Particularly,the role that the vanadium dioxide plays in the unit structure and the relevant principle are shown in detail.Then,based on the response of the unit structures contained vanadium dioxide,the overall design idea of the active control hologram is given clearly and the results from numerical simulation are also given to help explain.Finally,we introduce the fabrication and the experiment about the hologram as well as the holographic images of it in experiment.