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.