Abe, Marc

Following the Z scan of the cleaned viewport (see entry 2595) we decided to cross-check the relative alignment of the pump and probe laser using the surface reference sample.

We installed it and found out that it was quite misaligned (see figure 1)....

It means that over few days the alignment deteriorated quite a lot. We would really investigate how to get more stable alignment (maybe using similar mount provider as for the FC critical optics reported in entries 2583 2593)

We then spent most of the days trying to recover the proper alignment condition and finally reached the condition in figure 2.

To go from figure 1  to figure 2 we :

- checked the IU position (still 68 mm)

- checked the translation stage z position. By trying to have same amplitude of the lateral peaks in the AC signal we got z = 41.5 mm.

This gives us a new calibration factor :

ac = 0.4515 V
dc = 4.178 V
acdc = 0.108
p = 29.8 mW
R = 16.47 /W

Finally we reinstalled the cleaned viewport on the translation stage.