Effects of surface waves on the behavior of perfect lenses

Backwards-wave (BW) materials, which have simultaneously negative permittivity and permeability, support electromagnetic waves with phase propagation in the direction opposite to power flow. At an interface between BW materials and free space, the normal component of the wave vector changes sign. In the case of an evanescent wave, this leads to growth of the field amplitude inside the BW material. An infinite slab of an ideal, homogeneous BW material can simultaneously compensate the phase and the amplitude propagation of a wave, such that a point source is perfectly reconstructed in the image [J. B. Pendry, Phys. Rev. Lett. 85, 3966 (2000)]. However, it is more realistic to consider a thin layer at the surface over which the permeability and permittivity change from the free-space values to the BW values. Such layers influence the response of the system through a frequency shift of surface modes and the nonreflecting wave. One finds a lower bound for the size of resolvable features. It is shown that the transition layer is important even at thicknesses much smaller than the free-space wavelength of the radiation.