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. 
B. D. F. Casse, W. T. Lu, Y. J. Huang and S. Sridhar
physics.optics cond-mat.other