As what I showed in yesterday's report, through the CCD camera I can see the mode shape and power while I changed the output voltage of the PZT driver. So today I try to lock the cavity with different power, and found out if lock the cavity with the maximum of the TEM00 mode, I will lose the lock very soon, like in 5-10 mins. If I set the start point at some point near the maximum, the cavity will lock for longer period.
But it seems if I call the two modes near TEM00 as the previous mode and the next mode, the unlock always happened when the TEM00 move to the next mode, I think this means the PZT only let the mirror goes to one direction but I am not sure.
The other problems, the screen on the PZT driver shows the voltage it gives to the PZT, but during the lock process, it does not change. I think it is strange, because when there is fluctuation and the PZT will move to recover it, at this time,the number should change somehow.