In order to avoid polarization coupling when measuring birefringence with a tilted IR beam (the pump beam) we plan to take future measurement with the pump beam at normal incidence.

Yesterday I removed the last 2 steering optics on the 1310 nm beam path to have enough space to add 2 steering mirrors on the pump beam path.

I also installed a new power meter head (S146C) that has enough range to be used for both absorption and birefringence measurements.

I started by aligning the vertical direction using both a marker on a IR viewing card and iris.

Note that the injection table height is 28 cm with beam height of 5.5 cm and imaging table height is 24.5 cm (so beam height there should be 9cm).

Then I started to align the horizontal direction but it is slightly more tricky as the injection and imaging tables are not aligned.

I installed the razor blade and measured 1.5 deg incidence angle in this plane.

Today we will check the relative position of the blade with respect to the last steering mirror on the pump beam path to fine tune this incidence angle.