Extra ordinary optical transmission through sub wavelength hole arrays in cst -simula

hi
i want to simulate optical EOT in CST
I have taken the structure from the paper attached below
substrate height(quartz)-200nm
silver film-200nm
cylindrical holes: diameter -150nm , lattice parameter-900nm
Now how to choose the boundary conditions?
how to excite source?should i use waveguide port or choose proper boundary conditions?

tw-ebbsen.pdf
please help me....