基于双负介质结构单元的零折射率超材料

以连通长杆加树枝结构为基本单元模型,制备出折射率为零的超材料,并研究其电磁特性.首先考察了连通长杆加单级树枝的情况, 调节结构单元的几何参数可使其在频率f =9.5 GHz处实现有效介电常数和有效磁导率同时从负值趋于零点, 从而得到折射率n=0.同时也研究了单级树枝长度及夹角对零折射率超材料电磁参量的影响. 最后考察了树枝结构为二级和三级的情况,发现通过调节各单元的结构参数,均能得到在同一频率点处介电常数和 磁导率同时为零的零折射率超材料.

Zero-index metamaterial based on double-negative structure

We present a new kind of zero-index metamaterial composed of periodic array of dendritic cells with continuous long pole, and investigate its electromagnetic characteristics. First, we study the one-level dendritic cell with continuous long pole. The retrieved effective permittivity and permeability of the unit cell simultaneously tend to be zero from their negative values at a frequency of 9.5 GHz, which leads to a near-zero refractive index. Then by changing the geometric parameters of the unit, we find the influences of the branch length and the separation angle on the electromagnetic parameters. Finally, increasing the level number of the branch gives rise to two-level and three-level dendritic cells respectively with continuous long pole. Adjusting the geometric parameters of each unit cell to appropriate values, the zero-index matematerials with zero permittivity and permeability can be obtained at the same frequency.