Participant: Marco and Yuhang
We found a sudden movement of the mirror while we were doing the experiment. We think two mirrors are suspicious, which are used for coherent control laser alignment. Because the alignment of p-pol didn't change, we think the guess above is reasonable.
The suspicious mirrors are marked with black circles in the attachment. Next time, we should try to recover alignment by moving only one mirror. So that we can know which one is causing the problem and replace it.
The fork is properly fixed.