Periodic boundary condition


Can i use periodic boundary condition to find a mode in a simple silicon rib of 500nm*220nm waveguide?


Can you please elaborate on your inquiry? Why do you want to use periodic BCs?



I am trying to simulate one already published research article. In that article, they have optical mode in some silicon based hollow kind structure (same like rib) . I am not able to get same mode with pml or metal boundary condition. But it works for periodic BC. That is why i raised this query


Hi @phd1601102006

Periodic boundary conditions can be used for periodic structures. Is your structure periodic?

Maybe you can share the simulation file and paper with me for a review?



Any quantity which has certain repetition is periodic. Similar to this, continuous silicon rib is also periodic structure (with undefined period). That is the reason i am little bit confused about this.


Hi @phd1601102006

I am not still quite sure what your structure is. If you are simulating a structure like a photonic crystal fiber, you need to simulate the entire structure:

We use MODE to calculate the the supported modes in the cross section of waveguide. While the waveguide is infinitely long along the direction of propagation, it has a finite cross section and boundaries are generally set to metal or otherwise PML if you want to calculate the loss.