Thank you so much for your reply. I actually cannot find it from the GUI. Indeed, I cannot find it in the official file either. (The official file can be accessed via https://optics.ansys.com/hc/en-us/articles/360042800573-Inverse-Design-of-Grating-Coupler-2D-). Below is the screenshot of the mode monitor from the official file, there is no expansion for fom.
What I have done: first I added the description below under the model and then I can add this result into sweep manually and the result is fine.
temp = getresult("fom_exp", "expansion for fom");
T = -temp.T_backward;
So it seems that the results do exist and can be used for the sweep. But again it does not show in the GUI. From my lsf, I have linked the " fom " monitor to this mode expansion monitor. Below is the screenshot of my lsf and the setting inside the mode expansion monitor.
I reckon it will automatically generate the expansion for fom. Or are there any settings I should pay attention to?
Thank you again for your help! I am looking forward to hearing from you soon.