The Design Of Electromagnetically Induced Transparency Metamaterial Based On Toroidal Dipole Response

Electromagnetically induced transparency which usually produced by the destructive interference between electric dipole and magnetic dipole has been the hot spot of the researches,and is of great importance in fields such as sensing with high sensitivity and designing slow light device.Different from the two traditional electric dipole and magnetic dipole,the toroidal dipole is the third largest family and has been made the great improvement since being proved in experiment in 2010.It provides an effective way to design many different types of optical devices such as high Q resonator and resonance transparency devices because of its unique electromagnetic properties.In this thesis,we concentrate on studying the toroidal response in all-dielectric metamaterials and EIT based on toroidal resonance.The main contents are as follows:(1)An E-shaped all-dielectric EIT resonator is designed in the range of near-infrared wavelength.A high Q toroidal resonance can be excited when the electric field is polarized along the direction of the silicon rod which is vertically placed.Then the effects of the parameters of the structure on the toroidal response are analyzed and the maximum Q can up to 10~6.When we change the polarization direction of the electromagnetic wave into another,the metamaterial generates a wider magnetic resonance whose wavelength is the same as toroidal resonance.EIT appears by changing the symmetric structure into asymmetry,and is caused by the destructive interference between the toroidal dipole and magnetic dipole.At the same time,we analyse the effect of the asymmetric degree on the Q of EIT and realize the maximum group index up to 3000,which plays an important role in slow light devices.(2)An all-dielectric metamaterial toroidal resonator based on silicon rod array is studied.When the polarization of the incident electromagnetic wave is perpendicular to the length's direction of the dielectric rod,a sharp toroidal resonance with high Q factor can be excited.Besides,by adjusting the parameters of the silicon rod,the magnitude and Q factor of the resonance can be effectively controlled.(3)In near-infrared wavelength range,a metal-dielectric two layers metamaterial is designed to realize EIT.When the electric field of the incident electromagnetic wave is polarized along the length of the metal strip,the electric dipole and the toroidal dipole can be simultaneously excited,then the destructive interference between two bright modes generates the EIT effect.In addition,we emphatically analyze the effect of the distance between the metal layer and the dielectric layer on the properties of the EIT resonance.