The mixture of s- and p-polarization is set by a user-defined function (giving the fraction of s-polarization) which is accessible in a separate window. This window is opened by the Objects|Polarization command. Here you can define the function using the elements given in the technical notes. The default value for the fraction of s-polarization is 0.5, i.e. ideally unpolarized radiation is assumed.

Alternatively you can import data determined otherwise applying the Import command or simply use Drag&Drop to enter data from other sources, e.g. the Data Factory.