A Research On Terahertz Absorber With Dielectric Structure

The terahertz band,with its rich information,high security,presents an attractive application prospect to the world.This paper mainly researches terahertz absorbers based on dielectric structure.Traditional terahertz absorbers mostly achieve single-band,multi-band or narrow-band absorption,and some of them are based on patterned graphene structure,which is complicated to process and has certain edge effect.The terahertz absorber based on dielectric structure can realize ultra-wideband and high-performance absorption covering almost the whole terahertz band,which solves the problem that the traditional absorber can only absorb in narrow band,and its structure is relatively simple,which greatly reduces the production cost and time.Dielectric structure ultra-wideband absorber can be applied with terahertz involves energy collection,invisibility cloak,optical antenna,thermal imaging,detector,modulator,optical lenses,and other application research.In this paper,several kinds of terahertz absorbers with dielectric structure are set up,and the absorbing performance and absorbing mechanism of the absorber are analyzed.The main contents are as follows:1.A graphene-based absorber was designed based on dielectric loading.The semi-ellipsoid dielectric was combined with a single layer of graphene,and multiple discrete graphene-based plasma resonances(GPRs)and continuous multimode Fabry-Perot resonances were excited,thus achieving the ultra-wideband absorption of the absorber.The absorber achieved an ultrawide absorption bandwidth from 2 THz to more than 10 THz with an average absorption of 95.72%,and the relative bandwidth is133%.The absorbing mechanism of the electric field is explained,and the expression of?_N is deduced theoretically.The result confirms the simulation result.At the same time,the absorber has excellent wide-angle characteristics within the incident Angle range of50°.2.Based on the semi-ellipsoidal structure of the absorber,a hemispherical dielectric loaded graphene structure absorber was designed.The absorber achieved an ultrawide absorption bandwidth from 0.85 THz to more than 10 THz with an average absorption of 96.63%,and the relative bandwidth is 168%.Compared with the semi-ellipsoidal structure,the hemispherical structure has stronger absorption performance,the absorption bandwidth is increased by 1.15THz,the relative bandwidth is increased by 35%,and the average absorption is also increased by 0.91%.Because the hemispherical structure is rotationally symmetric,the absorption effect is the same under different polarization wave incidence,indicating that the hemispherical structure absorber is insensitive to polarization.3.A kind of Koch snowflake splitter absorber is designed.By using the width modulation of the splitter structure and cavity resonance,the absorber can realize wide band absorption.The simulation results show that the absorber has a absorption of more than 90% in the frequency range of 0.75THz-4.05THz,and the absorption bandwidth is3.3THz,and the relative absorption bandwidth can reach 137%.The structure maintains stable absorption in the range of incident Angle 50°and is insensitive to polarization.4.Design a load antireflection coating absorbing Koch snowflake fractal structure,and antireflection coating is to reduce the effect of reflection,absorption,thereby to increase the absorption,widen frequency band.The absorber has a absorption of more than 90% in the range of 0.9THz-6.4THz,the absorption bandwidth is 5.5THz,and the relative absorption bandwidth can reach 150%.Compared with the structure without anti-reflection coating,the bandwidth is increased by 2.2THz,and the overall absorption is also greatly improved.The structure maintains stable absorption in the range of incident Angle 60°and is insensitive to polarization.5.A kind of hollowed-out Koch snowflake type absorber is designed.The function of the hollowed-out structure design is to make the electromagnetic wave energy into the hollow groove and penetrate into the substrate for consumption,so as to improve the absorption of the absorber and broaden the frequency band.The simulation results show that the absorber has a absorption of more than 90%in the range of 0.6THz-10THz,the absorption bandwidth is 9.4THz,and the relative absorption bandwidth can reach 177%.The structure is also maintains stable absorption in the range of incident Angle 50°and is insensitive to polarization.6.The change of doping concentration of doped silicon will also affect the absorption performance of the absorber.The doping concentration can be changed by adding the energy intensity of the pumped beam.Therefore,the absorption effect can be improved dynamically by pumped beam.