Guilin Sun
Ansys Employee

Negative reflection: it means you illuminate the structure along positive axis direction. Its reflection is towards to negative direction. Since transmission is the integration of Poynting vector corss surface normal, and the surface normal is toward positive, thus the result is negative. You will need to add a mimus sign to the result.

Once you find the SPP wavelength, you can use a profile monitor to check the fields. However, it might be different from the SPP mode, which you can use a mode source at the specific wavelength to check the mode profile.