Investigation Of Surface Plasmons Based On Topological Insulator In Terahertz Regions

As a new optical material,Topological insulators(TIs)exhibit special kind of quantum electromagnetic properties.It is an insulative band structure,shows metal characteristics.Its spin is protected by the symmetry of time inversion.TIs have attracted a lot of attention because of their potential applications in quantum computing,spintronic devices,and especially in terahertz surface polaritons.Recent years,surface plasmon polaritons(SPPs)in topological insulators(Bi₂Se₃)have been studied in theoretically and experimentally.These studies are expected to make topological insulators as a promising candidate for the next generation of optoelectronic integrated devices.Meanwhile,the study of surface plasmon has also aroused great interest and enthusiasm,especially in the regulation of surface plasmon polaritons.However,the study of surface plasmons based on multilayer topological insulators in the terahertz band is still relatively small,and its absorption mechanism for terahertz waves needs to be further explored.In this paper,the surface conductivity of topological insulators(Bi₂Se₃)are investigated in firstly.Secondly,the equivalent dielectric function of the topological insulator film is further discussed,which is conducive to the in-depth study of the properties of the surface plasmon.Finally,via the analysis of its characteristics,a multi-layer U-shaped structure topological insulator is designed to achieve wide-band absorption in the terahertz frequency.The content of this article is divided into three parts:(1)The principle and characteristics of terahertz surface plasmons and the excitation of surface plasmons of different materials in the terahertz band are introduced.The characteristics,development and international research work of topological insulators are introduced in detail,especially the research status of topological insulators in the field of surface plasmon plasmons.(2)The characteristics of surface plasmons in topological insulators are analyzed.The special surface and internal optical properties of topological insulators are investigated,including the influencing factors of the electrical conductivity and dielectric coefficient of metallic surfaces.Based on the special optical properties of topological insulators,the characteristics of surface plasmons based on Bi₂Se₃is analyzed.(3)The excitation and absorption of surface plasmons based on topological insulators in the terahertz band are studied.The permittivity of topological insulators is described by the Drude-Lorentz model.Numerical modeling of one-dimensional grating structure and ring structure is carried out to confirm the reliability of simulation.The broadband absorption of terahertz waves by a multilayer Bi₂Se₃topological insulator film with a U-shaped structure is proposed and studied.