Design And Performance Of Broad-spectrum Terahertz Absorbing Structures Based On Metamaterials

Terahertz wave wavelength is between microwave and infrared wave,and its frequency ranges from 0.1 THz to 10 THz.It has many unique properties such as transmission,coherence,low energy.It has broad application prospects.Metamaterials are artificially constructed periodic subwavelength structures which have developed rapidly in recent years,with physical and electromagnetic properties that are not found in traditional materials in nature,including left-handed materials and photonic crystals.The properties of metamaterials are mainly determined by structural parameters.Adjusting the periodic unit structure can change the permittivity and permeability,and realize the regulation of electromagnetic waves.In this thesis,in order to improve the absorption performance of the device in the terahertz band,the metamaterial structure is combined with the terahertz technology.By designing metamaterial absorbers of various structures,a broad spectrum and high absorption are achieved.First of all,this thesis uses CST simulation software to study the absorption characteristics of the split ring structure,explore the number of split rings,ring width,ring spacing,silicon nitride layer thickness,polyimide layer thickness on the absorption characteristics.After parameter scanning and structure optimization,the periodic element structure size is finally selected as 36 ?m,the ring width,opening width,and ring spacing are all 2 ?m,and the outer diameter of the opening ring is selected as 5 ?m,9 ?m,13 ?m,17 ?m,patterned the thickness of the metal layer is 0.01 ?m,the thickness of the silicon nitride film is 0.4 ?m,the polyimide dielectric layer is 5 ?m,and the metal reflective layer is 2 ?m.The structure can achieve the design goal of broad spectrum and high absorption in the range of 2.47 THz?7.50 THz.Subsequently,a variety of combined structures were designed in this thesis,including disk-ring combined structure,fractal structure,nested structure,double-ring and rectangular-ring combined structure,double-layer structure,which achieved a wide range of incident electromagnetic waves within a specific frequency band.By setting the field monitor,the absorption occurrence site was observed.The angle and polarization insensitivity properties of the structure are verified by calculating the absorption characteristics at different incident angles in TE mode and TM mode,as well as at different phases.Finally,the designed samples were prepared by photolithography,magnetron sputtering and other methods,the surface morphology of the samples was observed by metallographic microscope,and the samples were tested by Fourier transform infrared spectrometer,and it was found that the test results match the simulation results well,basically achieve the design goal.