Eleonora P, Yuhang, Matteo, and Aritomi

Several months ago, we have already found the channel for AOM amplification was broken. And the work we did yesterday was without AOM working. Fortunately, Eleonora C remembers where is the old RF amplifier. And today we first implemented the old RF amplifier(ZHL-2). The amplification factor of it is 16dBm. The optimal RF signal for AOM should be 27dBm(while it converts too much to the first order). so usually, we use a lower value. So I give 7dBm from the signal generator and amplify it by 16dBm to have totally 23dBm of driving signal to AOM. The conversion efficiency is about 80% now.

Then, for sure, we need to do the alignment for green again. And then also for IR.

Another very important thing is the amplification of BAB(after OPO transmission). In the beginning, we were thinking to lock it with the same method for CC locking. But we observed noise level brought by the beat between BAB and CC. And this noise is almost 200 times larger than the coherent control error signal we have. So it is not possible to lock with CC beam. By following Matteo's suggestion, we used the leakage power from OPO s-pol transmission through PBS and to p-pol locking PD. Then we feedback this signal after giving an offset. And then we can basically lock the green phase and have a more stable IR beam going inside the filter cavity.

After all the work above, we could lock both green and IR again by changing the AOM driving frequency. We found make higher order modes and they are listed as follows.

The task of tomorrow will be to maximize the TEM00 by moving the last two steering mirrors on the bench for IR. And measure the height of each higher order modes. Also, maximize mode matching. We will follow the entry.