Scatterer on substrate problem

Dear all

Hello. I'm a beginner of COMSOL multiphysics.

I have tried to calculate the effect of nanostructure on light scattering.
Based on the user guide, "Scatterer on Substrate", I did it.
However, I'm still confused about the result.

I hope you give me some advice on that.

1. Results of 2-step simulation.
In the 1st simulation, total field simulation was perfomed without scatter.
And, the result was used as an background field of the 2nd scattered simulation.
Then what does emw2.normE or emw2.Ex (Ey, Ez) indicate?
Scattered field due to scatterer? or Total field?

2. Meaning of power flow of the relative fields?
I want to know the differences of power flow and power flow of the relative fields.
In addition, let me know some reference to understand how to derive the scattering cross section described in the user guide. ( surface interpolation of relative normal Poynting flux / Intensity of incident field)

3. If I want to calculate the intensity of back scattered wave due to the scatterer, which calculation do you recommend?
Is it okay to calculate the surface integration of power outflow?


I really hope that I can find some answer from you.
Thank you