Hi,
By NHA, do you mean nano-hole array? If so, the attached file may be interesting for you. It is one of our example files on a gold nano-hole array, simulated using periodic boundary conditions. It should not be difficult to adapt it to your needs by changing some dimensions and adding a thin dielectric layer to the top. Keep in mind 1 nm is pretty small, so you’ll want to use a smaller mesh and/or a non-uniform mesh. In which case, Lesson 22, will help you learn how to setup the non-uniform mesh.