Kyle
Ansys Employee

Hello,

An index monitor can be used to determine the refractive index in FDTD: https://optics.ansys.com/hc/en-us/articles/360034383134

You might find these grating coupler examples useful as well:

https://optics.ansys.com/hc/en-us/articles/360042305334  

https://optics.ansys.com/hc/en-us/articles/360042304774