Improved image quality of a Ag slab near-field superlens with intrinsic loss of absorption

Intrinsic loss of absorption in the Ag slab near-field superlens turned out to add a blurring effect to the ideal image reconstruction for the impedance match case. By optimizing the real part of the permittivity (ε′) of Ag, our FDTD calculation predicts ∼69% enhancement of visibility and ∼ 138% increased depth of field for the intensity contrast of 0.5 with similar focal spot size. For a near-field superlens with the higher absorption loss, the optimized image quality is obtained with a larger impedance mismatch, which can be realized by changing the wavelength of incident light for imaging.