The imaging properties of the metal superlens

The zero-refraction property of a metal film can be used to image so that the metal film behaves as a superlens. Experimentally, the metal superlens is sandwiched between the photosensitivity resist (PR) and the dielectric spacer in the photolithograph device to produce images. In this paper, the imaging conditions of the metal superlens, or the parameters of the device containing the superlens are investigated in detail. It is found that the energy zero-refraction effect is the intrinsic property of the metal superlens. The permittivities of the dielectrics at the two sides of the superlens will influence the imaging quality. The rule is drawn for obtaining best images: the two dielectrics should have the same permittivities, so-called symmetry case, and the real part of the permittivity of the metal superlens plus the dielectric permittivity is just equal to 1, i.e. ϵ(dielectric)+ϵr(superlens)=1.