Super-resolution imaging using a three-dimensional metamaterials nanolens

Abstract

Super-resolution imaging beyond Abbe’s diffraction limit can be achieved by utilizing an optical medium or “metamaterial” that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite medium possesses strongly anisotropic optical properties with negative permittivity in the nanowire axis direction, which enables the transport of both far-field and near-field components with low-loss over significant distances (>6λ), and over a broad spectral range. We demonstrate the imaging of large objects, having subwavelength features, with a resolution of at least λ/4 at near-infrared wavelengths. The results are in good agreement with a theoretical model of wave propagation in anisotropic media.