Modelling tapering and cross-talk
in I/O waveguide arrays
(with FIMMPROP)
The effect of tapering in the input and output waveguides in echelle
gratings can be
modelled using Epipprop combined with
FIMMPROP. This will allow you to characterise the amount of
unwanted cross-talk introduced by cross-coupling between neighbouring waveguides,
and the associated deterioration in performance for the echelle grating.
Spectra obtained with and without modelling the cross-coupling in the
case of a non-optimum waveguide array can be found below. You can see that the
cross-coupling introduces a fairly high level of cross-talk in the
output spectrum as the transmission peak becomes wider when the
cross-coupling in the taper is introduced (see arrow).
Impact of the waveguide cross-coupling on performance (left) output
spectra without taper model
(right) output spectra with taper model; notice the widening of the peak
pointed by the arrow
The corresponding Epipprop/FIMMPROP simulation showing the cross-coupling
in the input waveguide array is shown below.
Tapering and cross-coupling in I/O waveguide arrays
(top-left) XZ intensity profile in a tapered waveguide array showing unwanted cross-coupling
towards the end
(bottom-right) XY cross-section of the resulting Ex field launched in
the slab of the grating,
showing light coupled to the adjacent waveguides
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