Sub-wavelength imaging: Resolution enhancement using metal wire gratings

TL;DR

This paper demonstrates subwavelength imaging using a wire medium slab composed of parallel conducting cylinders, which enhances resolution by filtering out certain wave components, with experimental validation.

Contribution

It provides experimental evidence and theoretical analysis of resolution enhancement using wire gratings, showing no surface plasmons or resonant evanescent field enhancement.

Findings

Improved resolution observed with wire medium slab.

Wire gratings suppress traveling-mode components.

Enhancement applicable to near-field imaging.

Abstract

An experimental evidence of subwavelength imaging with a "lens", which is a uniaxial negative permittivity wire medium slab, is reported. The slab is formed by gratings of long thin parallel conducting cylinders. Taking into account the anisotropy and spatial dispersion in the wire medium we theoretically show that there are no usual plasmons that could be exited on surfaces of such a slab, and there is no resonant enhancement of evanescent fields in the slab. The experimentally observed clear improvement of the resolution in the presence of the slab is explained as filtering out the harmonics with small wavenumbers. In other words, the wire gratings (the wire medium) suppress strong traveling-mode components increasing the role of evanescent waves in the image formation. This effect can be used in near-field imaging and detection applications.