Today with Matteo we removed AZTEC #1 and repeated bulk calibration (R = 0.5769 cm/W) which is compatible with before.

Then, I installed a steering mirror to make the pump beam goes to the birefringence imaging unit.

Using the 2 razors blades I measured the beam position on the last steering mirror of the injection unit.

Then I move the razor blade as far as possible in z and place it in either horizontal or vertical where the beam is located on the last steering mirror.

Note that during the horizontal position tuning it is important to make sure that the beam is still aligned into the power-meter.

I then tuned both horizontal (fig 1) and vertical (fig 2) to reach angles of incidence of 0.014 and 0.006 deg respectively.

This is more than a factor 30 below the KAGRA precision requirement on the c-axis orientation so it is fine.

I connected s polarization to AC and p polarization to DC. (ie old lockin amplifier).

I reduced the laser power to about 359 uW so that we have at maximum about 1V on the lockin amplifier.

I tuned QWP and HWP (0.1 deg precision) to inject linear polarization :

hwp = 336.2 deg (s pol)
AC_min = 355/1e6
DC_max = 9.86*1/10

hwp = 21.2 deg (p pol)
AC_max = 746000/1e6
DC_min = 2.98*0.1/10

The PSD is far from saturating so maybe we could increase a bit the pump laser power and add attenuators before the lockin amplifier.