Research On Functional Devices For Electromagnetic Wave Regulation Based On All-dielectric Metasurfaces

The emergence of metasurfaces has increased the control methods for electromagnetic waves.However,with the improvement of the environmental applicability and functional requirements of metasurfaces,traditional metal-based metasurfaces have disadvantages such as large losses and poor environmental applicability.All-dielectric-based metasurfaces have become a research hotspot at home and abroad due to their simple structure,easy preparation,salt-alkali corrosion resistance,and strong environmental adaptability.In this paper,the research on functional devices for electromagnetic wave regulation based on all-dielectric metasurfaces is proposed,and the wave absorbing devices and beam regulation devices are designed from the perspective of electromagnetic wave amplitude regulation and phase regulation.The specific work is as follows:1.A multi-band wave absorber based on all-dielectric metasurface for electromagnetic wave amplitude regulation is proposed.Through the analysis of the electric field diagram,the special"I"-shaped cross structure of the absorber excites various resonant modes such as TE₁₂₀and TE₁₃₀,thus resulting in multi-band absorption.The absorber is then fabricated by 3D printing technology and tests experimentally using the NRL-arch reflectance test method under microwave anechoic chamber conditions.The numerical simulation and experimental results show that the device obtains five absorption fronts with an absorption rate of more than 90%in the range of 2GHz-12GHz,and the maximum absorption efficiency can reach 99.9%.2.A tunable absorber for electromagnetic wave amplitude regulation based on vanadium dioxide all-dielectric metasurface is proposed.Its structure consists of a silicon dielectric layer with a diagonal gap and a vanadium dioxide layer.The influence of the structure parameters of the absorber and the conductivity of vanadium dioxide on the absorption performance is studied by simulation.The change of the conductivity of the vanadium dioxide layer can affect the relative impedance matching effect of the absorber and free space.The numerical simulation results show that when the conductivity of vanadium dioxide increases fromσ=200S/m toσ=2000S/m,the absorbing performance of absorber is dynamically adjustable in the range of 1.41THz-1.64THz,and the absorption efficiency is above 90%.3.An all-dielectric metasurface-based beam steering for electromagnetic wave phase control is proposed.Its coding unit consists of a"X"shaped silicon dielectric column and a base.By introducing the principle of phase gradient coding,1-bit coding metasurface and 2-bit coding metasurface are successfully constructed by arranging coding units with different reflection phases through specific coding modes.In the 1-bit coding study,a bi-beam reflector is constructed with X_mand Y_ncoding modes coded in one direction,and a quadruple beam reflector is constructed with X_mY_ncoding modes code simultaneously in the x/y direction.In the study of 2-bit coding,a single beam deflector is constructed,and the coding and coding are convolved to expand the reflected beam to four azimuth angles of 45°,135°,225°,and 315°.4.A multifunctional tunable device based on vanadium dioxide metasurface for dual control of electromagnetic wave amplitude and phase is proposed.Its unit structure is composed of a"X"shaped silicon dielectric layer,a vanadium dioxide layer and a bottom silicon layer,and the multi-functional switching of the beam steering function and the wave absorbing function is realized by changing the conductivity of the vanadium dioxide layer.The regulation can be adjusted in real time;then in the 1-bit encoding,the X_mand Y_nencoding can be calculated through the operation of the encoding matrix to calculate the X_mY_nencoding method,which expands the application of the convolution theorem in the 1-bit encoding.When the conductivity of vanadium dioxide is changed,the function of beam modulation is changed to the function of wave absorption,and changing the distribution of its coding units can make the metasurface reach 90%absorption efficiency in the range of 0.35THz-0.66THz.