OptiFDTD Design and Simulation

Hello Iokesh,

I would need to see your design in order to provide the most relevant answer. If you could zip up your design and attach it then I can review it and see what may be the issue.

Without the design I will provide some feedback where I suspect the issue might be. Depending on which tutorial you are working from the atoms (the rods, what you want to be holes) and background material are set to:
– Atoms: WG_Example (channel) and WG_Example (material with n=2.5)
– 2D and 3D background: air
If you use the typical default values presented then you are going to get dielectric rods in air. To setup your simulation set the background of the simulation to be air and then set your atoms to a channel profile (One you create in the profile designer) that is air.

Scott

Hello Lokesh,

I had a chance to review your design and you will be relieved to know that your air hole design is in fact an air hole design. I believe where the confusion is coming from is that when looking at it in layout view it appears the same as the rod design. To really see what your discretized material looks like you can use the tab labelled “2D Refr_Idx-Re(y)” where you will see you have a background of 3.47 and an array of air holes, I have attached pictures of both views. Hopefully this clears things up for you.

Scott

My apologies Lokesh, I am not sure why those did not get attached. The images are from your “Holes Design 2.FDT” file
Scott

My interpretation of your original post was that you thought you were creating rods when you wanted to be creating air holes. The images I attached are showing you that your air hole design is in fact air holes.

When you are saying that are not getting what you want, what are you using as the basis for what you want? Are you looking at the simulation results and not satisfied with those results? If so what are you using as your reference? Are you confused why the air hole design does not show the same filtering behaviour as the rod design?

If that is the case it is because these filters rely on the structures bandgap and those two structures do not have the same bandgaps, you cannot simply make rods into holes, keep the r/a ratio, and expect the same behaviour. A good example of this is presented in Molding the Flow of Light. If you look at the 2D examples they provide the square array of dielectric rods and a square array of air holes in a dielectric and you will notice that they do not have the same band structure. In fact the rod based structures does not have a complete TE/TM bandgap while the hole based structure does.

Scott