Volumetric layered transmission-line metamaterial exhibiting a negative refractive index

We examine a new class of volumetric metamaterials based on two-dimensional (2D) transmission-line layers that exhibit a negative refractive index (NRI). The dispersion characteristics of a single 2D layer are revealed through a periodic analysis, and the effective-medium response of the volumetric layered topology is predicted by an intuitive equivalent circuit model. Dispersion and transmission characteristics are also obtained for various designs by using full-wave finite-element method (FEM) simulations, including one design meeting the requirements of Veselago's slab lens in free space, and suggest an isotropic NRI over bandwidths anywhere from 25% to 45%. Finally, the potential to implement these metamaterials from terahertz to near-infrared and optical frequencies is discussed.