Split-ring resonators hyperlens for undistorted sub-wavelength imaging

Hyperbolic metamaterials offer a unique solution to overcome the diffraction limit due to the ability of propagating high spatial frequencies [1]. To date, there have been several demonstrations of hyperbolic metamaterials that can convert evanescent fields into propagating waves based on their geometrical structure and therefore can be used as lenses [2-4]. The drawback of all the proposed hyperlenses is that the hyperbolic dispersion is given by the anisotropy of the permittivity only. This means that in such lenses only one of the propagating polarizations is non-diverging while the other (e.g., TE modes for a wire array) sees an “ordinary” material resulting in distorted images [4]. To overcome this limitation, a metamaterial which also has anisotropic permeability is necessary. Here, we propose a solution to this problem by realizing a hyperlens made of split-ring resonators (SRRs). In a first approximation, the SRRs behave as wires for transverse magnetic modes, and thus have anisotropic permittivity, and as magnetic resonators for transverse electric modes, and thus leading to anisotropic permeability. The resonators, made of tin in a Soda Lime glass matrix are fiber drawn, the target wavelength is 3 μm and magnification is achieved by tapering of the structure. Tapered, fiber drawn hyperlenses, based on wire arrays, have been reported in polymers for the THz spectral region [4] and in soft glass for the mid-IR [5]. Polymer fiber drawn SRRs and their behavior have been reported for THz frequencies [6,7].