Design And Simulation Of Terahertz Absorber Based On Electromagnetic Metamaterials

Electromagnetic metamaterials,which is a kind of artificial electromagnetic materials with the sub-wavelength scale periodic unit cell,have been widely studied in stealth,sensing,antenna and other field and other field owing to its unique physical properties that natural materials do not have.In the military field,with the rapid development of terahertz radar system,the traditional stealth technology has already not met the requirement of the future wars.Electromagnetic metamaterials that were invented provide an opportunity for the development and application of terahertz stealth material.At present researchers have introduced electromagnetic metamaterials into existing terahertz stealth materials,and fabricated a series of terahertz absorbers.However,the current terahertz absorber still has the disadvantages of low absorption efficiency,narrow bandwidth,complex structure and so on.In order to achieve terahertz stealth,this thesis explores broadband and multi-band metamaterials absorbers design methodology based on different structures and discussed the absorption characteristics of broadband and multi-band absorbers.The major working contents and results are listed below:1.On the basis of analyzing the influence of square and ring element structure parameters on absorption perforomance,this thesis presents broadband and multi-band metamaterials terahertz absorbers based double homo and double hetero composite structure layers.Using CST Microwave to analyze their absorption characteristics.The simulation results show that:(1)For the normal incidence,the bandwidth of double homo composite broadband terahertz metamaterials absorber is 0.642THz with the central frequency around 1.901THz;the bandwidth of double hetero composite broadband terahertz metamaterials absorber is 0.722THz with the central frequency around 2.041THz.(2)By calculating and analyzing the absorption spectra under different polarization angles and incident angle,it is concluded both broadband absorbers have the polarization insensitivity and wide-angle.(3)The physical mechanism of broadband absorption performance can be explained as the overlapping of multiple different resonance frequencies by analysis of magnetic field distribution and surface current distribution at different resonant frequencies.2.In this thesis,silicon column and air hole metamaterials multi-band absorbers were proposed.Using CST Microwave to analyze their absorption characteristics.The simulation results show that:(1)For the nornnal incidence,the silicon column metamaterials multi-band absorber have four peaks with the absorption coefficient all greater than 98%;the air hole metamaterials multi-band absorber have three peaks with the absorption coefficient all greater than 97%.(2)By calculating and analyzing the absorption spectra under different polarization angles and incident angle,it is concluded both multi-band absorbers have the polarization insensitivity and wide-angle.(3)The physical mechanism of multi-band absorption performance can be explained as silicon column and air hole excites a variety of standing wave mode.