Discussion Forum

Hi all,

I am using COMSOL 4.3 to simulate a 2D photonic crystal waveguide made of air holes in a dielectric (using the emw study of the RF module), and I wish to look at how roughness around the holes (as will be inevitable from the eventual fabrication) affects the confinement of light in the waveguide. I have been wondering how to create the surface roughness, and I have come up with two solutions, neither of which are desirable:

1) Using MATLAB, I can create a script which will give the x and y coordinates for an appropriate rough circle (using the random number generator in a clever way). This can be read in to COMSOL as an interpolation curve, and there we have the first rough circle. Now, we need many circles to create the crystal. The easy way out is just to copy the one random rough circle into an array, but this is in no way good enough.

2) Same as above, but with several circles. I.e., creating several txt files from the matlab script, and importing each into an interpolation curve. Ideally this should be done for each 'circle', but it might be way to time-consuming, depending on the size of the crystal. One idea here would be to create enough 'circles', and placing them in a 'random' way, while being careful not to get any periodicity in the placement (i.e., if we have circle 1,2,3, we would not like them placed 1 1 3 2 1 1 3 2, etc...).

Probably both of these solutions are just a substitute for actual knowledge of the geometry part of the simulation tool: There must be an easier way to do this? I would suspect that it is possible to create the geometry in CAD, and importing it to COMSOL: Is there an easier way to do this with CAD software? Any other ideas?

I sincerely appreciate any help on this!

Cheers,
Marius

Edit: It would be extremely nice if there was a way which would let me redefine the roughness (i.e. the expected frequency and amplitude of the error from a perfect circle) so I can find some threshold for when the light will be guided and not... Again, I will be grateful for any help on this one...