Bandstructure


#1

TE Bandstructure.fsp (402.5 KB)

Hello,

I am quite new to Lumerical and I have to simulate the bandstructure of the following structure that I have which is simply a substrate, a waveguide and a strip of gold on the side. I want to use TE mode for my simulation.
According to what i read on several pages, I have to use either electric or Magnetic dipoles at 0 or 90 degrees. Moreover I may need to apply symmetric boundary conditions, but in my case my structure isn’t symmetric.
I am uploading my file, please can you have a look at it and I would be glad if you can give me any suggestions to correct/improve my file.

thank you in advance


#2

Hi @sevag.abadian

If the cross section of the waveguide is not changing, you can run simulation in MODE to calculate effective index as a function of wavelength.
https://kb.lumerical.com/en/index.html?diffractive_optics_pcfibre.html

If the cross section changes and you know the mode of interest, then you can use mode source in FDTD:
https://kb.lumerical.com/en/index.html?pic_passive_bragg_initial_design_with_fdtd.html

If you want to obtain a complete bandstructure for a waveguide where the cross section varies, then you can use dipole sources:
https://kb.lumerical.com/en/index.html?diffractive_optics_pc_waveguides.html

For your structure, you can use MODE/FDE. This can be also done in FDTD and you can use mode source.

If you have any further questions, please share the schematic of your design and why you are using Matrix transformation and I will be glad to be of a help.

Thanks


#3

Hello

thank you for your answer,

1-My bad, the matrix transformation shouldn’t be there for the time being.
2-So for my complete structure it’s a waveguide with a periodic grating beside it. So that is why
a- I want to see the bandstructure without the periodicity
b- then change the strip of gold to gratings and see the difference
I want to know if the dipoles that I have used are in the right direction and if the mesh is good or it requires more refinement.

Thank you again,

Sevag


#4

Hi @sevag.abadian

Assuming that the current geometry is correct (I am not sure why gold in not on the top of BIG structure and which direction light will be propagated) and you want to run simulations in FDTD:

  1. Add a mesh override over the gold layer and make sure that the gold cross section is a multiple integer of mesh cells.
  2. Use sources with different polarizations (by changing theta and phi) to make sure that all the modes are excited.

I hope this was helpful.