Focusing of a light beam below the diffraction limit by the combination of an aperture and a photonic crystal (PC). (a), (b) demonstrates the results obtained with the effective medium theory and (c), (d) for a periodic square air-hole lattice PC. In (a) the spatial spectrum is plotted after the aperture (red) and after the PC (green) demonstrating the amplification of evanescent components. In (a), (b) the spatial distribution of energy density with a FWHM of 0.23 lambda and in (c) the distribution of the field inside and in the vicinity of the PC are shown.