There is a little discrepancy between the 2 ways we compute the s to p polarization losses.
One possible explanation could be that we were using the mean of theta and delta n from 7 measurements during about 5 days.
It is quite probable that alignment condition or translation stage position slightly drifted between each measurements making this mean value a bit different with some sharp features.
I attach to this entry the comparison between the direct estimation of losses and the delta n and theta computed for each input polarization angle.
There is no sharp feature anymore and we have better agreement between the 2 estimations !