How to apply polarized E-field?

My question is simply "how to apply polarized E-field to z-axis?"
I mean the incident wave should be polarized Ex or Ey.

p.s how can i fix below problem?

Failed to find a solution.
Singular matrix.

For mesh-case 0 there are 1 void equations (empty rows in matrix) for the variable mod1.emw.S1x.
at coordinates: (0,0,0), ...
and similarly for the degrees of freedom (empty columns in matrix).
Returned solution is not converged.