In this appendix we state the asymptotic far-field Green functions for a planarly layered medium. It is assumed that the source point r0 = (x0, y0, z0) is in the upper half-space (z > 0). The field is evaluated at a point r = (x, y, z) in the far-zone, i.e. r ≫ λ. The optical properties of the upper half-space and the lower half-space are characterized by ε1, μ1 and εn, μn, respectively. The planarly layered medium in between the two halfspaces is characterized by the generalized Fresnel reflection and transmission coefficients. We choose a coordinate system with origin on the topmost surface of the layered medium with the z-axis perpendicular to the interfaces. In this case, z0 denotes the height of the point source relative to the topmost layer. In the upper half-space, the asymptotic dyadic Green function is defined as

where p is the dipole moment of a dipole located at r0 and G0 and Gref are the primary and reflected parts of the Green function. In the lower half-space we define

with Gtr being the transmitted part of the Green function. The asymptotic Green functions can be derived by using the far-field forms of the angular spectrum representation.

The primary Green function in the far-zone is found to be

The reflected part of the Green function in the far-zone is

where the potentials are determined in terms of the generalized reflection coefficients of the layered structure as

The transmitted part of the Green function in the far-zone is

where δ denotes the overall thickness of the layered structure.