Guilin Sun
Ansys Employee

" we will be simulating a wavelength up to 0.7 um"

"the wavelengths used are very large (100-300um)"

Not sure exactly what wavelength you are talking. Related issues have been discussed various times in different posts.

Since the background material is lossless, the monitor location does not affect the transmitted power;

you can place the monitor anywhere you want, as long as you know exactly what the result means to you.

Once again, the distance between PML and the device is to prevent any possiblility that the near fields interact with PML. If there is no local neaar fields such as non-rdiative, evanescent waves or SPP, the distance can be smaller.