Index Modulation

[flying lingcod]

Hi everyone,
In optigrating software,When we define the parameters of the grating, we can see the Ind.Mod. option in the Grating Definition dialog box. And in the use guide, we can see the official definition:
Ind. Mod. In the Index Modulation box, you define the amplitude of the index modulation of the grating.
So i want to know how to calculate the index modulation(Ind.Mod), and how the index modulation affect the transmission spectrum.
Thank you all!

[Amin Khorshidahmad]

Hi,
Index modulation affects both the bandwidth and amplitude response of the grating. You may have a look at “Coupled-mode theory for guided-wave optics” by Yariv or coupled mode theory in any text book, e.g. Photonics by Yariv & Yeh, for details and quantitative analysis.

Kind regards,
Amin

[flying lingcod]

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

[Author]

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