Dynamic Modulation And Polarization Characteristics Of Electromagnetically Induced Transparency In Metamaterials

Metamaterials,kind of artificial design electromagnetic materials,have some special physical characteristics that natural materials don’t have,such as negative refraction,negative conductivity and negative magnetic permeability,etc.Terahertz wave is located between microwave and infrared wave.Besides some characteristics of microwave and infrared wave,terahertz wave also has low photon energy,which can be applied to the detection of biological tissues and cells.Terahertz wave can also be applied to the fields related to communication whose communication rate that cannot be achieved by microwave.This thesis mainly studies the electromagnetically induced transparency effect generated by metamaterials in terahertz band.The research contents are mainly divided into the following aspects:(1)A metamaterial designed with copper is studied by vertical incident terahertz wave and the physical origin of electromagnetically induced transparency effect effect was analyzed.Furthermore,the influence of geometric parameters of metal structure on the transmission spectrum is explored.(2)A double U structure metamaterials was proposed.Terahertz waves passing through the structure have polarization-dependent characteristics.By changing the polarization angle,the transmission spectrum will change.In particular,the multichannel electromagnetically induced transparency effect is obtained.Moreover,Fano resonance is found in the specific frequency range of some polarization angles.Fano resonance is used to study the characteristics of biosensor,and it is found that it has high sensitivity.A center-symmetric metamaterial structure is also designed,which is insensitive to the polarization of incident light.(3)Dynamic modulation has become a hot topic in the study of electromagnetically induced transparency effect.In this paper,the electromagnetically induced transparency effect is dynamically controlled by external pump light.The materials used for dynamic control are optically controlled silicon and phase change material vanadium dioxide.Silicon and vanadium dioxide are both photosensitive materials.By changing the environmental condition,the electrical conductivity of silicon and vanadium dioxide will change,which will cause the change of transmission spectrum.In this paper,active control of transmittance spectrum is studied by using silicon and vanadium dioxide,the regulation of transmittance reached 61.8% and 68.2% respectively.The size of group delay is also explored,and the results can be helpful to the manufacture of slow light retarder.