Thank you very much, I’m so sorry for my late response. Something wrong with my computer, I have been unable to log in to the forum last month.
I have learned the coupled mode theory, According to the coupled mode theory, when κL=π/2 is satisfied, there is maximum power transmission between the core and the cladding, but I still can’t deduce the numerical relationship between κ and the refractive index modulation (Ind.Mod)
Best regards