Electromagnetic Properties Of Dual Left-handed Bands Meatmaterials

Left-handed meta-materials (LHM) is a kind of artificial electromagnetic material in which both the permittivity and permeability are simultaneously negative. Theory and experiment research of meta-materials is a hot topic in physics and electromagnetic area in recent years, because the unique electromagnetic properties in meta-materials. Since Smith etc obtained the LHM in microwave frequency with wires and split rings for the first time in year of 2001, a amount of new structures based on SRRs-wires have been proposed, i.e. the S-shaped structure, theΩ-shaped structure, the H-shaped structure, the rod pairs structure and the fishnet structure etc, the left-handed properties have been obtained from GHz all the way to optical frequencies. The fishnet meta-materials which has "metal-dielectric-metal" sandwich structure with holes has simple shape and can be obtained left-handed properties whether excitation wave is vertical or inclined. Since it can be fabricated use nano-technology and easy form 3D meta-material through stacking, it's considered of the best design meta-materials which can work in high frequency. Currently, the fishnet structure meta-materials which working in the frequencies from microwave to optical have been confirmed. However, there is only one left-handed pass-band in the traditional fishnet structure.In this thesis, based on the traditional rectangular fishnet meta-material, we arrange linearly and alternately, respectively, two kinds of structural unit with different permittivity of dielectric spacers. The electromagnetic properties for both fishnet structures are numerical investigated. The main results obtained are as follows:Through numerical investigate for the both fishnet structures, the following conclusions are drawn:1). We use two different dielectric coefficient in linearly structure. There are only two transmission peaks which corresponding to different unit in the linearly structure, respectively.2). We use two different dielectric coefficient in alternately structure. There are more (than two) transmission peaks when the difference between the dielectric coefficient is large.3). The effective electromagnetic parameters retrieved from the simulated S-parameter results confirmed the left-handed pass-band. The behaviors of negative refractive index in both fishnet metamaterials are further validated by the simulation of a wedge-shaped model and the backward wave propagation.4). The transmission peaks are all red-shifted in the two units fishnet structure compared to the traditional fishnet structure.