A.Taflove's book "Computational Electrodynamics" explains well about dispersion in numerical schemes. But how can numerical wavenumber be actually be calculated, when only spatial steps and timesteps are know?
All analysis made so far are for free space. For waveguides, velocity changes to a specific phase velocity of a propagating mode. But what if more than one modes are propagating at once?
can't understood the free space 1-d scheme. Like in case of an optical waveguide we consider an varying index (difference) that change (under certain boundary condition)
result in multiple mode that propagates through the guide. (if depending factor are only either wavelength & index & radius )
I can only think of complex analysis in 3d varying effect of index or radius on multiple propagating mode