On Mon, 12 Mar 2007, #YIP CHAN HOE# wrote:
I am trying to figure out the decaying function of gaussian-src or
continuous-src, and hope to hear your advice.
The default source end-time[] is infinity (never turn off) according to
MEEP reference.
And, the default cutoff[] is 3.0 and it is the number of widths the
current decays for before we cut it off and set it to zero.
Question
(1) The question is how do the current decays when the source never turn
off ?
For continuous-src, the cutoff refers to the decay backwards in time, i.e.
as the current slowly turns on. If you specify a non-zero width, then the
continuous-src slowly turns on with a tanh-like shape, and cutoff
specifies where the tail of the tanh is cut off at t=start-time.
(2) I am guessing it is probably due to PML, but where in the geometry
do MEEP consider the current to be decaying ?
The parameters in continuous-src and gaussian-src only affect the time
dependence of the source (the decay in time, etcetera). They have nothing
to do with the *spatial* dependence of the source, which is determined by
the parameters of the (make source ...) (in particulary, by size and
amp-func).
Steven
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