How to set PML parameters with metal?

Hi,
im using Rsoft fullwave package to calculate propagation of surface plasmon in
metal-air-metal waveguide (the same structure in the attached paper), I
want to get the transmission spectrum at the output of the waveguide, here I meet
some problems, is anyone can help me?

1. I feel very confused about the parameters setting of the boundary condition.
here I use PML with a reflection coefficient of 1e-8 as the BC and it is
attached to the metal (Ag), but the result is terrible(see the attached picture)
, it seems a lot of light is reflected from the boundary and cause the error? I
dont know why, can PML attach to metal? How should I set the width and
reflection coefficient of the PML to get the right result? When I increase the
width to more than 1 micrometre, the software warns that the area of the PML is
larger than 70% and the result may be imprecise... My simulation file is attached below, please change back the file type from .jpg to .pdf.

2. how can I get the transmission spectrum at the output of the waveguide? I
dont know how set the time monitor to get the power normalized to the incident
light, If any one is familiar with the software, please help me.

Thanks a lot!

I think you can change both the reflection coefficient and the PML width at the same time in order to make the absorption condition enough to absorb the light.

Also, when you change the grid size and the time step accordingly, the reflection change as well.