Dear Matt

Thank you for the advice. I could figure it out myself, if I know how the POLARIZATION parameter is interpreted or defined. 

Where can I find that information? I found this on my own: 

"This card specifies the direction of the electric field of the incident beam, or the main axis of the ellipse in the case of elliptical polarization. x, y, z are the coordinates of the nonzero polarization vector"

But I lack a definition of the coordinate system - the polarization direction with respect to what, exactly?