Experimental demonstration of negative index of refraction
  We introduce an improved and simplified structure made of periodic arrays of pairs of H-shaped metallic wires that offer a potentially simpler approach in building negative-index materials. Using simulations and microwave experiments, we have investigated the negative-index n properties of these structures. We have measured experimentally both the transmittance and the reflectance properties and found unambiguously that a negative refractive index with Re(n)<0 and Im(n) <Re(n). The same is true for epsilon and mu. Our results show that H-shaped wire pairs can be used very effectively in producing materials with negative refractive indices. 
Jiangfeng Zhou, Thomas Koschny, Lei Zhang, Gary Tuttle and Costas M.   Soukoulis