Yuhang and pierre

This work is motivated by the difficulty of locking the GRMC loop.

We measured again the loop, we found the resonant peaks have changed relative to the original measurement.

The first peak was changed from 7.23kHz to 6.9kHz and the second peak was changed from 11.85kHz to 9.9kHz.

We have already investigated by changing the position of clamps. But the peak position was not changed. However, I didn't try to move the end mirror of the mode cleaner. The change of these peaks position is still not clear.