While waiting for measurement, I started to analyze data and found out that our measurements are clipped.

Indeed I forgot to change the Y center position of the sample while, to switch from absorption to birefringence, we add 2 steering mirrors that shift quite a lot the beam.

I checked the sample surfaces by looking at the position that minized both the s and p polarization power.

I measured Y_center = 160.37 mm and restarted measurements.