High numerical aperture and low-loss negative refraction based on the fishnet rich anisotropy

In this paper we report both numerical and experimentally high numerical aperture on a mesostructure based on fishnet-like building blocks. Under the indefinite media framework, we are able to identify a negative refraction never cutoff band (3rd band of the extraordinary transmission metamaterial) with low-losses at millimeter-waves. We relate negative refraction with the diffraction modes of the periodic structure. The work is another step forward in the new but rapidly evolving subfield of negative refraction metamaterials by anisotropy. The breadth and utility of this approach suggests that metamaterials at their meso-scale may circumvent the problem associated to narrowness and losses exhibited by negative refractive index media at their subwavelength domain, while still being away from the wavelength scale of electromagnetic band-gap.