Design And Theoretical Analysis Study Of The Metamaterial Terahertz Device

As the unique frequency range and spectrum characteristics of terahertz(THz)waves,THz technology has become the research hotspot in many applications of modern science and technology,national economy and national defense construction.With the deepening development and extensive application of THz technology,the urgent necessary of the research on various THz devices has been proposed.As a new type of artificial composite materials,metamaterials,with the exotic physical properties such as negative refractive index,ultra-high resolution and ultra-wide spectrum response,provide the new opportunities for the development of terahertz devices.Based on metamaterials,this paper carries out the researches of THz devices such as absorber,polarizer and plasma-induced transparency(PIT)structure.The main contents are as follows:(1)A multi-band PIT device based on a split metal ring structure is proposed and studied.The device is composed of two plasma-induced transparent substructures,which own the different bright-dark mode coupling distances generating the independent single frequency bands individually.The device realizes three transparent windows in the range of 0.6 and 1.8THz,and the window transmittance is greater than 80%.In this work,the center frequency of the transparent window of the PIT structure changes with the refractive index of the upper measured object.By adding photosensitive silicon to the split,moreover,the amplitude of the transparent window changes with the light intensity.The results show that this structure possesses eminent sensing performance and the slow light effect(the maximum delay up to 4ps).(2)An ultra-wideband terahertz absorber based on the double-arc structure is proposed and investigated.This structure operates in the frequency range of 0.59-1.31 THz with a relative absorption bandwidth of 76%while the absorption rate is greater than 90%.Furthermore,this work can operate with the insensitivity of polarization and incident angle.Finally,the experimental measurement has been developed and the measurement results are consistent with the simulation results.(3)A broadband line-circular polarizer based on the double-layer structure of the zigzag line is designed and investigated.In the frequency range of 0.4 and 1.0 THz(the relative bandwidth approximates 52%),the polarizer realizes broadband linear-to-circular polarization conversion with the axial ratio AR<3dB.Compared with the single-layer structure,the double-layer structure increases the phase difference between two perpendicular components and realizes a narrow-band line-circular polarization conversion.Due to the introduction of the metal sheet,the bandwidth of the phase difference is broadened and thereby that of the axial ratio AR<3dB is broadened.Then the experimental measurement has been developed.The results show that the measurements are in good agreement with the simulation.