Previous measurements of Shinkosha7 were taken before we updated our calibration procedure.

I performed again the birefringence measurements with the updated calibration.

First I reinstalled the 2 steering mirrors and realigned the IR beam. I measured vertical AOI = 0.003 deg and horizontal AOI = 0.000 deg.

I tuned the HWP and QWP to minimize the power in reflection of the readout PBS.

Then, I took 10mn measurements while injecting s then p polarization.

Fig 1 reports our calibration factors. Also we have an error of 4e-4 on the p and s polarization estimation.

Then, I installed the sample and took measurement from 0 deg input polarization angle (s polarization) up to 75 deg with 15 deg increment.

For some measurements, I was worried about saturation so I repeated such measurement with larger lockin amplifier range.

The measurements are reported from fig 2 to 7.

The birefringence parameters are shown in fig8. The wrapping of dn and theta is highly visible.

Actually, it is possible to unwrap dn as shown in fig9 but this assumes that all our degeneracy comes from delta n and not theta while in reality it is a combination of both.

I think that this is the reason why we have some 'peaks' in delta n that seem to be present only for some input polarization angle.