Participant: Marco and Yuhang

Since the locking of coherent control PLL plays a very important role in getting a coherent control error signal. When we want to perform coherent control, we suffered a lot from the bad locking condition.

Then we start to consider why we cannot lock coherent control PLL. At some point, we realize, even we used an attenuator to reduce minor peaks. But the PLL system still tries to bring it to these minor peaks. So we decide to remove the attenuator. Now the situation is that the beat note comes from fiber PD and then has an amplification of 18dB.

In this case, we can lock coherent control PLL much better. The locking scheme(named as PLL_CC20190221) is saved in the default folder of all the PLL settings. And the parameters are listed in the attached figure.