We propose a concept of a near-field lens capable of reliably imaging deep-subwavelength objects at a distance of several times the thickness of the lens. Nearly flat guided modes in a high-index dielectric slab are shown to propagate information of evanescent waves emanating from the imaged object, thus providing the degree of detail needed to map fine spatial variations. A practical way of implementing the proposed flat lens is theoretically demonstrated using closely packed metal nanoparticles giving rise to large effective permittivities in the spectral region right to the red of the plasma frequency. We perform rigorous electromagnetic simulations showing that realistic absorption levels in the metal are still compatible with deep-subwavelength spatial resolution.
Christensen, J., & García de Abajo, F. J. (2010). Slow plasmonic slab waveguide as a superlens for visible light. Physical Review B Condensed Matter, 82(16), . https://doi.org/10.1103/PhysRevB.82.161103