Employment of metamaterial cloaks to enhance the resolution of near-field scanning optical microscopy systems based on aperture tips

Abstract

In this paper, we numerically demonstrate that plasmonic covers designed through the scattering cancellation approach can be successfully used to enhance the performance of near-field scanning optical microscopy (NSOM) systems based on the employment of aperture tip probes. The material used to partially cover the tip exhibits a near-zero value of the real part of the permittivity function at the working frequency and is designed in such a way to dramatically reduce the undesired electromagnetic coupling between the sample to be imaged and the metallic coating of the aperture tip. We show that minimizing such an unwanted interaction may lead to enhance the maximum achievable resolution of the NSOM system. The approach proposed is numerically tested at optical frequencies through a proper set of full-wave simulations, taking into account material losses and frequency dispersion. The proposed results represent a proof-of-concept and can be scaled at lower frequencies (infra-red and THz), where fabrication issues are more relaxed and possible implementation can be made practical using alternating plasmonic/non-plasmonic multi-layers or even some natural materials.