This is a continous work from 3717 (date: 2024.09.06)

I locked the PCC with GR laser by feeding back the signal into frequency actuator of the laser. The locking was stable, no weird behaviour at 667 Hz. The firt png is the open loop gain.

Still 667 Hz peak exists (second png). I guess this peak originates from the piezo actuator, hindering feedback locking at the same time. I will try bonding again.