$consider3dipoles

$consider3dipoles is the command to decide if the emission light is a pure dipole source and the ratio of Px, Py, and Pz.

$consider3dipoles
Px Py Pz

Px, Py, Pz are the ratio of Px, Py, Pz dipole. They should be positive values.
After 3 values are set, the possibility to emit x-polarized diople Px would be

$R_{Px} = \frac{Px}{Px+Py+Pz}$

And the Py and Pz would be

$R_{Py} = \frac{Py}{Px+Py+Pz}$
$R_{Pz} = \frac{Pz}{Px+Py+Pz}$

The $consider3dipoles setting in GUI interface is here
Press Ray Tracing, check the box, and fill in the field for the Px, Py and Pz as needed!