December 6, 2022 at 10:21 pmJiahui HuangSubscriber
Hello, I have a problem with the results of doing Fourier transform of the field distribution of a L3 cavity. The starting example I use is:https://optics.ansys.com/hc/en-us/articles/360041567754 and I change the cavity to a L3 cavity and obtain the field distribution of the fundamental mode from the mode monitor as below:
and if I use log scale on the field magnitude, I notice that there is finite field at the edge
Then I apply the 2D Fourier transform in Matlab using
Y = fft2(X);
where X is the field distribution of above image.
I got the below result and I think the center bringth region is an artifact from the Fourier transfrom of a rectangle due to the finite field magnitude on the edge (see field distribution in log scale mentioned above):
Then I decide to increase the amount of holes so that the field decays sufficiently on the edge and the resulting field distribution in log scale is below:
And you can see that the field decays to smaller values on edge thanks to increased amount of holes. However when I do Fourier transform on this one, I still obtained a center bright region with even larger value
I would appreciate if you have any comments on how to get rid of the center bright region!
December 9, 2022 at 7:41 pmGuilin SunAnsys Employee
Fourier transform requires the field intensity to be zero at the monitor edge. You will need to smoth the field data. Please refer this example: Equi-frequency contours of photonic crystal
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