Amrita Pati
Ansys Employee

Hi Ekaterina,

I tested your code. In this case, you should include, one interface at 0 microns, second at 0.12 microns and third at 0.22 microns. The substrate and superstrate should not be included as interfaces. But the simulation region should extend into the substrate and the superstrate so that the simulation knows which medium the light is incident from and which medium it is transmitted to. The schematic is shown below:

That being said, as you said the index results provided by RCWA seem to be inconsistent. The co-ordinates seem to be shifting depending upon the location of the simulation region which is unusual whereas the FDTD index monitor is returning the expected results as shown below. This might be due to a bug. I will investigate it further and get back to you as soon as I can.