Quoting "Steven G. Johnson" <[EMAIL PROTECTED]>:
You have a gaussian centered on 0.15 with a width of 0.3, which is
pretty wide. When the pulse is this wide (in frequency), you can
observe a computational detail: Meep's Gaussian pulse is not actually
precisely a Guassian, it is the derivative of a Gaussian
If I'm not wrong, the derivative of a gaussian would look very
different ! I guess you mean something else.
(this ensures that there is no net charge left in the computational
cell after the pulse is gone, which prevents divergences in some
cases with periodic boundaries). The difference between the two is
small except for very broad Gaussians in frequency (short pulses in
time).
Yes, that's what I observed too.
Because the main reason to use a short pulse is to get a
broad-spectrum response, and you have to normalize such a response by
the input spectrum anyway as explained in the manual, the exact shape
of the spectrum shouldn't actually matter.
Well, what I want to do is to cover a very big range of frequency. So
what I wanted to do is to cut this big range in few smaller ones. Then,
for each of those smaller range, simulate with a pulse centered in it
with a FWHM corresponding to the size of the range.
So I have two question now instead of one ;)
First, how short the pulse can be ? I guess at least bigger than the
resolution in time but how much ?
Second, in case I can't cover the range I'm interrested in with one
pulse only (and anyway maybe, cause we never know), what is the
expression for the gaussian pulse, or it's Fourier transform, or the
expression for the resulting central frequency and width as a function
of the given ones ?
Best regards.
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