Figure 3: Imaging of two dipole sources.

(a,b) The corresponding far-field images of two point dipoles that are located at 24 and −24 nm, respectively, from the origin within the gap are clearly resolvable with a separation of 672 nm, (c) when increase the gap size to 24 nm, the resolution decreases and the two image points cannot be resolved. (d) The loss of the metal is evaluated. The blue curve represents a cross-section of an image of a dipole located 8 nm from the centre with a lossless metal. The red curve corresponds to the dielectric constants of −2+i. The cross-section widens and resolution reduces, and the centre shifts slightly towards the origin.