Marc, Yuhang

Yesterday, when we just entered the cleanroom, we realized that the main laser head was quite hot (by hand). However, we found the laser was fine (the laser was on, and we could lock SHG). So we didn't care so much about that.

However, after we used the main laser for a short period, the main laser suddenly went off. Almost one week ago, we reported the main laser sudden off. We didn't know the reason. In total, we found three times of laser off in the recent month.

After the laser suddenly off, we found that we couldn't turn it on by pressing the switch. So we put a thermal meter on top of the laser head and wait for a while. Figure 1 shows the laser head temperature change during this waiting time. Then we turned the main laser key off. After turning it on, the laser starts to work well.

Recently we found another issue related to the main laser. More than two years ago, we did an investigation of our main laser stability (elog). After three hours of operation, laser power becomes very stable. But now, even after one day, the power stability is not very ideal. Figure 2 shows this laser power change. Although this is not a big issue for squeezing production since its frequency is quite low, this may mean we are having small problems.

After switching the laser on, we monitored laser power again and found laser head temperature increases back. Figure 3 shows this laser power change. This temperature change is related to the laser power change since they have almost the same frequency. We will check this coherence in the future.