Katsuki-san, Marc

We removed all the readout of the birefringence. The reason being that the photodetectors size was quite small wrt to the beam size. This means that performing the alignment without sample might not be so accurate for the case with sample.

First we replaced the optical breadboard from imperial holes size to metric ones.

Then we reinstalled the PBS, the ODs and tried to installed the new PSD (PDQ80A) that have quite larger sensor size but are also sensitive to visible light.

In order to have a larger beam on the PSD, we replaced the lens in front of the PBS by a 100 mm focal one.

Sadly, because the PSD sensor is 4 cm above the screwing hole, it was quite tricky to find proper post.

Therefore, we also installed 2 steering mirrors just after the ODs.

Finally, we installed laserline filters right in front of the PSDs.

We took time to put label on various cables.

The alignment was checked (ie we confirmed that the maximal power of both ac and dc is reached without sample).

I just started birefringence measurement of the TAMA T1 sample with s polarization at the input.

The 'bad news' is that the gain of the PSD requires to change the gain of both lockin amplifiers depending on the input polarizations.