Research On Terahertz Wave Directional Reflector Based On Phase Transition Characteristics Of Metamaterial

The ultra-surface structure device based on two-dimensional metamaterial has the advantages of low cost,lightness and integration,and has important application prospects and value in the terahertz frequency band.In this paper,the research on metasurfacebased circularly polarized broadband reflective devices is carried out,focusing on the phase characteristics based on metasurface elements and the directional reflectors and focussers constructed by metasurface elements.The main work of this paper is as follows:First,based on the phase characteristics of the metasurface structure,the dielectric layer thickness and dielectric constant of the metasurface unit based on the metalinsulator-metal(MIM)structure are discussed in the case where the circularly polarized wave is used as the vertical incidence of the feed.For the influence of the phase characteristics of the unit,the metasurface reflection efficiency of the single-ring metal patch metasurface and the "1"-shaped metal patch is compared,and the latter is obviously much higher than the reflection phase of the former,and then the analysis of the different resonance point pairs of the unit corresponding effects of phase,summarizing the method of designing metasurface elements with different phase differences.The second is to carry out the theory and simulation research of terahertz metasurface directional reflector.Based on the phase characteristics of the metasurface unit,19 metasurface units with a phase difference of 90° to 360° are constructed to form a line structure and a 19×16 array structure reflector.The reflection angle of the reflector is expected to be 19.74°.Simulation results show that in the frequency range of 0.35 THz-0.51 THz,the reflection angle is 20°,the reflection coefficient is 0.72-0.86,and the reflection efficiency is good.The simulation results are basically consistent with the theoretical expectation.The third is to study the terahertz metasurface wide-band focusing reflector,designed to work in the frequency band of 0.37 THz-0.5 THz,the numerical aperture is 0.291,and the focal length is 40 mm.The phase of the unit is composed of the phase of the geometric phase rotation unit and the resonance phase of the adjustment resonance point,which can be superimposed on each other,and the two do not affect each other.The former phase is independent of the operating frequency and can constitute the basic phase of the focus reflector,and then It is related to the working frequency and is used to compensate the phase chromatic aberration of different frequencies.The metasurface wide-band focusing reflector was simulated and analyzed by a simplified model.The simulation results were basically consistent with the theoretical expectations.