I want to understand how to apply EigenMode expansion method (http://www.photond.com/files/docs/PW03_eme_paper.pdf) for beam propagation on a system of lenses.
The interface between two mediums of different refraction index is modelled as a scattering matrix between the incoming and outgoing intensities on each side of the boundary. But i'm not clear if this includes cases where the interface is curved, as is the case for optical lenses. How does the medium curvature gets accounted at computing the scattering matrix coefficients?
Is there an example i can see about how to compute them?