# Slot waveguide and its equivalent strip waveguide

#1

Dear @bkhanaliloo / @aalam,

I know that SWG (sub-waveguide grating) can be defined by an equivalent strip waveguide having same cross-section of the SWG blocks and the refractive index of neq = nclad +𝛿 (ncore-nclad) (𝛿 – duty cycle of gratings).
My question is: ‘Is there any similar way of equivalent representation of slot waveguide by a strip waveguide?’ ‘How do I calculate an equivalent refractive index of strip waveguide?’

I would appreciate your help.
thank you.

#2

Dear @ktwayana

Thank you for reaching out.

I was trying to refer you a recent case where we tried to use equivalent refractive index for slot waveguide, and I realized that you are the owner of that topic! My understanding is that while in some cases we can do some sort of averaging to simplify the problem, but generally it gets complicated when we have a gap in the structure.

In one of our webinars, this problem is mentioned (watch this video, minutes:11:00–12:30). It looks like using cladding refractive index might be useful, but I am not quite sure if this trick will work in every cases.

#3

Dear @bkhanaliloo,
Thank you very much for your time and suggestion.