Theoretical And Experimental Research Of The Cross-polarization Filter And The Multi-peak EIT Phenomenon In Metamaterials

Metamaterials exhibit dramatical physics characteristics and hold huge potentials in various applications since its permittivity and permeability can be simultaneously negative.Under certain conditions, asymmetrical metamaterials could reveal Fano reronances mimicking electromagnetically induced transparency (EIT) in quantum systems. More importantly, we can easily achieve the EIT-like phenonenon from microwave to optical range based on metamaterial, thus we can avoid many complex conditions and troubles when studying the EIT phenonenon in atomic media. Fano resonances in metamaterials show asymmetric line shape and steep dispersion characteristics, which promises many applications such as sensing, switching, slow light, active device and polarization converter. Therefore, in this thesis we focus on designing and investigating Fano-resonanat metamaterials, further studying polarization conversion and electromagnetically induced transparency phenomenon,and presenting theoretical and experimental results. The main contents and innovations are given as follows:(1) We propose a new type of cross-polarization filters. We present numerical simulations and comprehensive analysis to show how the structure parameters, material parameters and incident polarization directions affect on Fano resonances. The results show that we can achieve high-Q frequency selective devices by decreasing losses of the dielectric substrates and appropriately optimizing metamaterial structures and also effectively modulate the Fano resonances by changing the polarization directions of incident waves.(2) We propose a planar metamaterial with coaxial multiple metallic rings. We studied the polarization effect in the double-ring metamaterial that is attributed to the different contributions of the electric and magnetic components in the two different cases of TE and TM incident waves. At the same time, we numerically and experimentally investigated the electromagnetic responses of the multiple-ring structures. Excitation of the trapped mode resonance arises from strong coupling and the scattering field cancellation of two adjacent rings in the multiple-ring metamaterial, resulting in transparent EIT-like transmission windows. The number of the transparent EIT-like windows is directly related to the the number of rings.