KAGRA MIR (Polarization)
SimonZeidler - 16:57, Wednesday 10 November 2021 (2733)
Comment to TAMA 1 (Shinkosha) birefringence measurement (Click here to view original report: 2731)

That looks very good, indeed!
What you can do in addition is to check for the second (negative) solution according to theory, as I reported last meeting.

An important point is also to be very precise with all input parameters. For example, it isn't enough to set the thickness to just 6cm or so but to take into account the refraction due to the inclination and the hence extended beam path.