  We describe the change of the spatial distribution of the state of
polarisation occurring during two-dimensional imaging through a multilayer and
in particular through a layered metallic flat lens. Linear or circular
polarisation of incident light is not preserved due to the difference in the
amplitude transfer functions for the TM and TE polarisations. In effect, the
transfer function and the point spread function that characterize 2D imaging
through a multilayer both have a matrix form and cross-polarisation coupling is
observed for spatially modulated beams with a linear or circular incident
polarisation. The point spread function in a matrix form is used to
characterise the resolution of the superlens for different polarisation states.
We demonstrate how the 2D PSF may be used to design a simple diffractive
nanoelement consisting of two radial slits. The structure assures the
separation of non-diffracting radial beams originating from two slits in the
mask and exhibits an interesting property of a backward power flow in between
the two rings.
