Robust method to determine the resolution of a superlens by analyzing the near-field image of a two-slit object

In the last decade, metamaterials-based superlenses, with a resolution below Abbe's diffraction limit, have emerged. To obtain a rough estimate of the resolution of such superlenses, imaging of two subwavelength slits, separated by a subwavelength gap \textit{d} is typically performed. The resolution $\Delta$ of the lens corresponds to the minimum possible gap $d_{min}$ for which a distinct image of the two slits can be resolved ($\Delta \sim d_{min}$). In this letter, we present a more quantitative estimate of the resolution of manufactured lenses by fitting analytical near-field image profiles, obtained from imaging a two-slit object with a theoretical negative-index lens of known resolution, to experimental data. We conclude the discussion by applying our analytical method to 3 case examples of superlensing from the literature. As shown, this method is particularly attractive for rapidly assessing the performance of fabricated superresolution lenses.