Directed sub-wavelength imaging using a layered metal-dielectric system
  We examine some of the optical properties of a metamaterial consisting of thin layers of alternating metal and dielectric. We can model this material as a homogeneous effective medium with anisotropic dielectric permittivity. When the components of this permittivity have different signs, the behavior of the system becomes very interesting: the normally evanescent parts of a P-polarized incident field are now transmitted, and there is a preferred direction of propagation.   We show that a slab of this material can form an image with sub-wavelength details, at a position which depends on the frequency of light used. The quality of the image is affected by absorption and by the finite width of the layers; we go beyond the effective medium approximation to predict how thin the layers need to be in order to obtain subwavelength resolution. 
B. Wood, J. B. Pendry, D. P. Tsai