Hello Jing,
You are going to need to provide a bit more information than simply needing field enhancement. FDTD is an incredibly powerful and flexible tool but before you begin putting stuff into it you need to be very clear about what it is your are modelling and what information you are trying to extract. Typically for an E/Eo result you would run your simulation with (E) and without (Eo) the structure to show what kind of field enhancement you get by having the structure there.
Scattering and everything else will depend on exactly what you are looking for and what kind of system you are trying to model. Simply having your design file all I know is you have a periodic array of cylinders. Is there a paper you are working from?
I have briefly looked at your design file and for a start I can discuss your input plane. It is recommended that input plane should never be placed right on top of a boundary. That is a PML designed to introduce loss with no reflections, a source right there will not work as expected. Additionally your device is also right on the input plane and the boundary. Is your source supposed to be inside the rod or is this supposed to be an input plane impinging on it?
Scott Newman